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Document And Entity Information - USD ($) $ in Billions	12 Months Ended
Document And Entity Information - USD ($) $ in Billions	Dec. 31, 2012	Feb. 15, 2013	Jun. 30, 2012
Document and Entity Information [Abstract]
Entity Registrant Name	ARCH COAL INC
Entity Central Index Key	0001037676
Document Type	10-K
Document Period End Date	Dec. 31, 2012
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	FY
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 1.4
Entity Common Stock, Shares Outstanding		212,246,799

Consolidated Statements Of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Statement [Abstract]
Revenues	$ 4,159,038	$ 4,285,895	$ 3,186,268
Costs, expenses and other
Cost of sales	3,438,013	3,267,910	2,395,812
Depreciation, depletion and amortization	525,508	466,587	365,066
Amortization of acquired sales contracts, net	(25,189)	(22,069)	35,606
Change in fair value of coal derivatives and coal trading activities, net	(16,590)	(2,907)	8,924
Coal derivative settlements, non-hedging	(43,990)	7	(4,542)
Selling, general and administrative expenses	134,299	119,056	118,177
Contract settlement resulting from Patriot Coal bankruptcy	58,335
Legal contingencies	(79,532)
Mine closure and asset impairment costs	523,568	7,316
Goodwill and other intangible asset impairment	346,423
Acquisition And Transition Costs		47,360
Gain on Knight Hawk transaction			(41,577)
Other operating income, net	(20,219)	(10,941)	(15,182)
Total operating expenses	4,840,626	3,872,319	2,862,284
Income (loss) from operations	(681,588)	413,576	323,984
Interest expense, net:
Interest expense	(317,626)	(230,186)	(142,549)
Interest income	5,478	3,309	2,449
Interest expense, net	(312,148)	(226,877)	(140,100)
Other nonoperating expense:
Net loss resulting from early retirement and refinancing of debt	(23,668)	(1,958)	(6,776)
Bridge financing costs related to ICG		(49,490)
Other nonoperating expense, Total	(23,668)	(51,448)	(6,776)
Income (loss) before income taxes	(1,017,404)	135,251	177,108
Provision for (benefit from) income taxes	(333,717)	(7,589)	17,714
Net income (loss)	(683,687)	142,840	159,394
Less: Net income attributable to noncontrolling interest	(268)	(1,157)	(537)
Net income (loss) attributable to Arch Coal, Inc.	$ (683,955)	$ 141,683	$ 158,857
Earnings per common share
Basic earnings (loss) per common share	$ (3.24)	$ 0.75	$ 0.98
Diluted earnings (loss) per common share	$ (3.24)	$ 0.74	$ 0.97
Weighted average shares outstanding
Basic, weighted average shares outstanding	211,381	190,086	162,398
Diluted, weighted average shares outstanding	211,381	190,905	163,210
Dividends declared per common share	$ 0.20	$ 0.43	$ 0.39

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net income (loss)	$ (683,687)	$ 142,840	$ 159,394
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax	(14,523)	4,271	9,814
Net amount reclassified to income	918	1,665	101
Pension, postretirement and other post-employment benefits, reclassifications into net income	(13,605)	5,936	9,915
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	(1,924)	114	1,841
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Net of Tax	4
Unrealized gains (losses) on available-for-sale securities	(1,920)	114	1,841
Unrealized gains (losses) on derivatives	4,320	2,913	221
Reclassifications of (gains) losses into net income	2,653	(10,563)	1,514
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax	6,973	(7,650)	1,735
Total other comprehensive income (loss)	(8,552)	(1,600)	13,491
Total comprehensive income (loss)	$ (692,239)	$ 141,240	$ 172,885

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2012	Dec. 31, 2011
Current assets
Cash and cash equivalents	$ 784,622	$ 138,149
Restricted cash	3,453	10,322
Short term investments	234,305
Trade accounts receivable	247,539	380,595
Other receivables	84,541	88,584
Inventories	365,424	377,490
Prepaid royalties	11,416	21,944
Deferred income taxes	67,360	42,051
Coal derivative assets	22,975	13,335
Other	92,469	110,304
Total current assets	1,914,104	1,182,774
Coals, lands and mineral rights	6,218,776	6,578,430
Plant and Equipment	3,391,265	3,225,985
Deferred mine development	1,079,856	1,064,279
Property, Plant and Equipment	10,689,897	10,868,694
Less: Accumulated Depreciation, Depletion and Amortization	(3,352,799)	(2,919,544)
Property, plant and equipment, net	7,337,098	7,949,150
Other assets
Prepaid royalties	87,773	86,626
Goodwill	265,423	596,103
Equity investments	242,215	225,605
Other	160,164	173,701
Total other assets	755,575	1,082,035
Total assets	10,006,777	10,213,959
Current liabilities
Accounts payable	224,418	383,782
Coal derivative liabilities	1,737	7,828
Accrued expenses and other current liabilities	318,018	348,207
Current maturities of debt and short-term borrowings	32,896	280,851
Total current liabilities	577,069	1,020,668
Long-term debt	5,085,879	3,762,297
Asset retirement obligations	409,705	446,784
Accrued pension benefits	67,630	48,244
Accrued postretirement benefits other than pension	45,086	42,309
Accrued workers' compensation	81,629	71,948
Deferred income taxes	664,182	976,753
Other noncurrent liabilities	221,030	255,382
Total liabilities	7,152,210	6,624,385
Redeemable noncontrolling interest		11,534
Stockholders' Equity
Common stock	2,141	2,136
Paid-in capital	3,026,823	3,015,349
Treasury stock, at cost	(53,848)	(53,848)
Retained earnings	(104,042)	622,353
Accumulated other comprehensive loss	(16,507)	(7,950)
Total stockholders' equity	2,854,567	3,578,040
Total liabilities and stockholders' equity	$ 10,006,777	$ 10,213,959

Balance Sheet Parenthetical (Parentheticals) - $ / shares	Dec. 31, 2012	Dec. 31, 2011
Statement of Financial Position [Abstract]
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	260,000,000	260,000,000
Common Stock, Shares, Issued	213,759,000	213,183,000

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Dec. 31, 2009	$ 2,115,106	$ 1,643	$ 1,721,230	$ (53,848)	$ 465,934	$ (19,853)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income attributable to Arch Coal, Inc.	158,857				158,857
Pension, postretirement and other post-employment benefits	9,814
Net amount reclassified to income	101
Unrealized losses on available-for- sale securities	1,841
Unrealized gains on derivatives	221
Net amount reclassified to income	1,514
Total comprehensive income (loss)	172,293					13,436
Dividends, Common Stock	(63,373)				(63,373)
Issuance of shares of common stock under the stock incentive plan — restricted stock and restricted stock units, net of forfeitures	0	0	0
Issuance of shares of common stock under the stock incentive plan — stock options including income tax benefits	1,764	2	1,762
Employee stock-based compensation expense	11,717		11,717
Share-based Compensation	11,717
Ending Balance at Dec. 31, 2010	2,237,507	1,645	1,734,709	(53,848)	561,418	(6,417)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income attributable to Arch Coal, Inc.	141,683				141,683
Pension, postretirement and other post-employment benefits	4,271
Net amount reclassified to income	1,665
Unrealized losses on available-for- sale securities	114
Unrealized gains on derivatives	2,913
Net amount reclassified to income	(10,563)
Total comprehensive income (loss)	140,150					(1,533)
Dividends, Common Stock	(80,748)				(80,748)
Issuance of shares of common stock under the stock incentive plan — restricted stock and restricted stock units, net of forfeitures	0	2	(2)
Issuance of shares of common stock under the stock incentive plan — stock options including income tax benefits	2,316	2	2,314
Employee stock-based compensation expense	10,882		10,882
Share-based Compensation	10,882
Stock Issued During Period, Value, New Issues	1,267,933	487	1,267,446
Ending Balance at Dec. 31, 2011	3,578,040	2,136	3,015,349	(53,848)	622,353	(7,950)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income attributable to Arch Coal, Inc.	(683,955)				(683,955)
Pension, postretirement and other post-employment benefits	(14,523)
Net amount reclassified to income	918
Unrealized losses on available-for- sale securities	(1,924)
Unrealized gains on derivatives	4,320
Net amount reclassified to income	2,653
Total comprehensive income (loss)	(692,512)					(8,557)
Dividends, Common Stock	(42,440)				(42,440)
Noncontrolling Interest, Change in Redemption Value	(5,474)		(5,474)
Issuance of shares of common stock under the stock incentive plan — restricted stock and restricted stock units, net of forfeitures	0	0	0
Issuance of shares of common stock under the stock incentive plan — stock options including income tax benefits	5,131	5	5,126
Employee stock-based compensation expense	11,822
Share-based Compensation	11,822		11,822
Ending Balance at Dec. 31, 2012	$ 2,854,567	$ 2,141	$ 3,026,823	$ (53,848)	$ (104,042)	$ (16,507)

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating activties
Net income (loss)	$ (683,687)	$ 142,840	$ 159,394
Adjustments to reconcile to cash provided by operating activities:
Depreciation, depletion and amortization	525,508	466,587	365,066
Amortization of acquired sales contracts, net	(25,189)	(22,069)	35,606
Noncash mine closure and asset impairment costs	515,491	7,316
Goodwill and other intangible asset impairment	346,423
Bridge financing costs related to ICG		49,490
Amortization relating to financing activities	20,238	14,067	10,398
Net loss resulting from early retirement of debt and refinancing activities	23,668	1,958	6,776
Prepaid royalties expensed	22,650	34,842	34,605
Employee stock-based compensation expense	11,822	10,882	11,717
Gain on Knight Hawk transaction			(41,577)
Changes in:
Receivables	113,531	(74,914)	(7,287)
Inventories	9,468	(50,900)	5,160
Coal derivative assets and liabilities	(13,158)	6,079	9,554
Accounts payable, accrued expenses and other current liabilities	(171,580)	52,191	87,807
Income taxes, net	27,545	(21,759)	(1,364)
Deferred income taxes	(336,036)	10,519	(12,405)
Increase (Decrease) in Asset Retirement Obligations	(42,531)	3,868	23,997
Other	(11,359)	11,245	9,700
Cash provided by operating activities	332,804	642,242	697,147
Investing activities
Acquisition of ICG, net of cash acquired		(2,894,339)
Capital expenditures	(395,225)	(540,936)	(314,657)
Additions to prepaid royalties	(13,269)	(29,957)	(27,355)
Proceeds from dispositions of property, plant and equipment	22,825	25,887	330
Purchases of short term investments	(236,862)
Proceeds from Sale of Short-term Investments	1,754
Investments in and advances to affiliates	(17,758)	(61,909)	(46,185)
Purchase of noncontrolling interest	(17,500)
Change in restricted cash	6,869	5,167
Consideration paid related to prior business acquisition		(829)	(1,262)
Cash used in investing activities	(649,166)	(3,496,916)	(389,129)
Financing activities
Proceeds from the issuance of senior notes	359,753	2,000,000	500,000
Proceeds from term note	1,633,500
Proceeds from the issuance of common stock, net		1,267,933
Payments to retire debt	(452,934)	(605,178)	(505,627)
Net increase (decrease) in borrowings under lines of credit and commercial paper program	(481,300)	424,396	(196,549)
Payments on term note	(7,625)
Net payments on other debt	(682)	5,334	82
Debt financing costs	(50,568)	(114,823)	(12,751)
Dividends paid	(42,440)	(80,748)	(63,373)
Issuance of common stock under incentive plans	5,131	2,316	1,764
Proceeds from Noncontrolling Interests			891
Cash provided by (used in) financing activities	962,835	2,899,230	(275,563)
Increase (decrease) in cash and cash equivalents	646,473	44,556	32,455
Cash and cash equivalents, beginning of period	138,149	93,593	61,138
Cash and cash equivalents, end of period	784,622	138,149	93,593
Cash paid during the year for interest	310,241	213,697	134,866
Cash refunded (paid) during the year for income taxes, net	$ 28,057	$ (7,094)	$ (36,765)

Accounting Policies	12 Months Ended
Accounting Policies	Dec. 31, 2012
Accounting Policies [Abstract]
Accounting Policies	Accounting Policies Basis of Presentation The consolidated financial statements include the accounts of Arch Coal, Inc. and its subsidiaries and controlled entities (the “Company”). The Company’s primary business is the production of thermal and metallurgical coal from surface and underground mines located throughout the United States, for sale to utility, industrial and export markets. On June 15, 2011, the Company acquired International Coal Group, Inc. (“ICG”). The Company currently operates 15 mining complexes in West Virginia, Kentucky, Maryland, Virginia, Illinois, Wyoming, Colorado and Utah. In addition, the Company has a metallurgical coal mine in development in West Virginia. All subsidiaries are wholly-owned. Intercompany transactions and accounts have been eliminated in consolidation. The Company's subsidiary Arch Western Resources, LLC (“Arch Western”) operates coal mines in Wyoming, Colorado and Utah. On April 9, 2012, Delta Housing, Inc., a subsidiary of BP p.l.c. and a joint venture partner in Arch Western, exercised their contractual right to require the Company to purchase their 0.5% common and their preferred membership interests in Arch Western. With the payment of the negotiated purchase amount of $17.5 million on July 2, 2012, Arch Western became a wholly-owned subsidiary. Accounting Pronouncements There are no accounting pronouncements whose adoption had, or is expected to have, a material impact on the Company's consolidated financial statements. Accounting Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and revenues and expenses in the accompanying consolidated financial statements and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates. Cash and Cash Equivalents Cash and cash equivalents are stated at cost. Cash equivalents consist of highly-liquid investments with an original maturity of three months or less when purchased. At December 31, 2012 and 2011, the carrying amounts of cash and cash equivalents approximate their fair value. Allowance for Uncollectible Receivables The Company establishes an allowance for uncollectible receivables for the amounts of trade accounts receivable and other receivables that are not expected to be collected, based on past collection history, the economic environment and specified risks identified in the receivables portfolio. Receivables are considered past due if the full payment is not received by the contractual due date. At December 31, 2012 and 2011, there was either no allowance or an insignificant allowance for uncollectible receivables. Inventories Coal and supplies inventories are valued at the lower of average cost or market. Coal inventory costs include labor, supplies, equipment costs, transportation costs incurred prior to the transfer of title to customers and operating overhead. The costs of removing overburden, called stripping costs, incurred during the production phase of the mine are considered variable production costs and are included in the cost of the coal extracted during the period the stripping costs are incurred. Investments and Membership Interests in Joint Ventures Investments and membership interests in joint ventures are accounted for under the equity method of accounting if the Company has the ability to exercise significant influence, but not control, over the entity. The Company's share of the entity's income or loss is reflected in other operating income, net in the consolidated statements of operations. Information about investment activity is provided in Note 8, "Equity Investments and Membership Interests in Joint Ventures." Marketable equity and debt securities held by the Company that do not qualify for equity method accounting are classified as available-for-sale and are recorded at their fair value on the balance sheet. Unrealized gains and losses on these investments are recorded in other comprehensive income or loss. A decline in the value of an investment that is considered other-than-temporary would be recognized in operating expenses. Prepaid Royalties Leased mineral rights are often acquired through royalty payments. When royalty payments represent prepayments recoupable against future production, they are recorded as a prepaid asset, with amounts expected to be recouped within one year classified as current. When the coal is mined under these leases the royalties are recouped and the prepayment is charged to cost of sales. Acquired Sales Contracts Coal supply agreements (sales contracts) acquired in a business combination are capitalized at their fair value and amortized over the tons of coal shipped during the term of the contract. The fair value of a sales contract is determined by discounting the cash flows attributable to the difference between the contract price and the prevailing forward prices for the tons under contract at the date of acquisition. See Note 4, "Acquired Sales Contracts" for further information related to the Company's acquired sales contracts. Exploration Costs Costs to acquire permits for exploration activities are capitalized. Drilling and other costs related to locating coal deposits and evaluating the economic viability of such deposits are expensed as incurred. Property, Plant and Equipment Plant and Equipment Plant and equipment are recorded at cost. Interest costs incurred during the construction period for major asset additions are capitalized. We capitalized $15.6 million of interests costs during the year ended December 31, 2012, while the amounts capitalized in the years ended December 31, 2011 and 2010 were insignificant. Expenditures that extend the useful lives of existing plant and equipment or increase the productivity of the asset are capitalized. The cost of maintenance and repairs that do not extend the useful life or increase the productivity of the asset are expensed as incurred. Preparation plants and loadouts are depreciated using the units-of-production method over the estimated recoverable reserves, subject to a minimum level of depreciation. Other plant and equipment are depreciated principally using the straight-line method over the estimated useful lives of the assets, limited by the remaining life of the mine. The useful lives of mining equipment, including longwalls, draglines and shovels, range from 5 to 32 years. The useful lives of buildings and leasehold improvements generally range from 10 to 30 years. Deferred Mine Development Costs of developing new mines or significantly expanding the capacity of existing mines are capitalized and amortized using the units-of-production method over the estimated recoverable reserves that are associated with the property being benefited. Costs may include construction permits and licenses; mine design; construction of access roads, shafts, slopes and main entries; and removing overburden to access reserves in a new pit. Additionally, deferred mine development includes the asset cost associated with asset retirement obligations. Coal Lands and Mineral Rights Rights to coal reserves may be acquired directly through governmental or private entities. A significant portion of the Company's coal reserves are controlled through leasing arrangements. Lease agreements are generally long-term in nature (original terms range from 10 to 50 years), and substantially all of the leases contain provisions that allow for automatic extension of the lease term providing certain requirements are met. The net book value of the Company's coal interests was $5.1 billion and $5.6 billion at December 31, 2012 and 2011. Payments to acquire royalty lease agreements and lease bonus payments are capitalized as a cost of the underlying mineral reserves and depleted over the life of proven and probable reserves. Coal lease rights are depleted using the units-of-production method, and the rights are assumed to have no residual value. Future lease bonus payments total $83.4 million in 2013, $67.3 million in 2014, $60.0 million in 2015, and $60.0 million in 2016. Depreciation, depletion and amortization. The depreciation, depletion and amortization related to long-lived assets is reflected in the statement of operations as a separate line item. No depreciation, depletion or amortization is included in any other operating cost categories. Impairment If facts and circumstances suggest that the carrying value of a long-lived asset or asset group may not be recoverable, the asset or asset group is reviewed for potential impairment. If this review indicates that the carrying amount of the asset will not be recoverable through projected undiscounted cash flows generated by the asset and its related asset group over its remaining life, then an impairment loss is recognized by reducing the carrying value of the asset to its fair value. The Company may, under certain circumstances, idle mining operations in response to market conditions or other factors. Because an idling is not a permanent closure, it is not considered an automatic indicator of impairment. Goodwill In a business combination, goodwill represents the excess of the purchase price over the fair value assigned to the net tangible and identifiable intangible assets acquired. The Company tests goodwill for impairment annually as of the beginning of the fourth quarter, or when circumstances indicate a possible impairment may exist. If the results of the testing indicate that the carrying amount of a reporting unit exceeds the fair value of the reporting unit, the fair value of goodwill must be calculated. An impairment loss generally would be recognized when the carrying amount of goodwill exceeds the implied fair value of goodwill, determined by subtracting the fair value of the other assets and liabilities associated with the reporting unit from the total fair value of the reporting unit. The fair value of a reporting unit is determined using a discounted cash flow ("DCF") technique. A number of significant assumptions and estimates are involved in the application of the DCF analysis to forecast operating cash flows, including the discount rate and projections of selling prices and costs to produce. See additional discussion in Note 7, "Goodwill." Deferred Financing Costs The Company capitalizes costs incurred in connection with new borrowings, the establishment or enhancement of credit facilities and the issuance of debt securities. These costs are amortized as an adjustment to interest expense over the life of the borrowing or term of the credit facility using the interest method. The unamortized balance of deferred financing costs was $101.5 million and $90.5 million at December 31, 2012 and 2011, respectively. Amounts classified as current were $17.3 million and $15.8 million at December 31, 2012 and 2011, respectively. Current amounts are recorded in other current assets and noncurrent amounts are recorded in other assets in the accompanying consolidated balance sheets. Revenue Recognition Revenues include sales to customers of coal produced at Company operations and coal purchased from third parties. The Company recognizes revenue at the time risk of loss passes to the customer at contracted amounts. Transportation costs are included in cost of sales and amounts billed by the Company to its customers for transportation are included in revenues. Other Operating Income, Net Other operating income, net in the accompanying consolidated statements of operations reflects income and expense from sources other than physical coal sales, including: bookouts, the practice of offsetting purchase and sale contracts for shipping convenience purposes, and contract settlements; royalties earned from properties leased to third parties; income from equity investments; gains and losses from dispositions of assets; and realized gains and losses on heating oil derivatives that do not qualify for hedge accounting and are not held for trading purposes. Asset Retirement Obligations The Company's legal obligations associated with the retirement of long-lived assets are recognized at fair value at the time the obligations are incurred. Accretion expense is recognized through the expected settlement date of the obligation. Obligations are incurred at the time development of a mine commences for underground and surface mines or construction begins for support facilities, refuse areas and slurry ponds. The obligation's fair value is determined using a DCF technique and is based upon permit requirements and various estimates and assumptions that would be used by market participants, including estimates of disturbed acreage, reclamation costs and assumptions regarding equipment productivity. Upon initial recognition of a liability, a corresponding amount is capitalized as part of the carrying value of the related long-lived asset. The Company reviews its asset retirement obligation at least annually and makes necessary adjustments for permit changes as granted by state authorities and for revisions of estimates of the amount and timing of costs. For ongoing operations, adjustments to the liability result in an adjustment to the corresponding asset. For idle operations, adjustments to the liability are recognized as income or expense in the period the adjustment is recorded. Any difference between the recorded obligation and the actual cost of reclamation is recorded in profit or loss in the period the obligation is settled. See additional discussion in Note 14, "Asset Retirement Obligations." Derivative Instruments The Company generally utilizes derivative instruments to manage exposures to commodity prices. Additionally, the Company may hold certain coal derivative instruments for trading purposes. Derivative financial instruments are recognized in the balance sheet at fair value. Certain coal contracts may meet the definition of a derivative instrument, but because they provide for the physical purchase or sale of coal in quantities expected to be used or sold by the Company over a reasonable period in the normal course of business, they are not recognized on the balance sheet. Certain derivative instruments are designated as the hedge instrument in a hedging relationship. In a fair value hedge, the Company hedges the risk of changes in the fair value of a firm commitment, typically a fixed-price coal sales contract. Changes in both the hedged firm commitment and the fair value of a derivative used as a hedge instrument in a fair value hedge are recorded in earnings. In a cash flow hedge, the Company hedges the risk of changes in future cash flows related to a forecasted purchase or sale. Changes in the fair value of the derivative instrument used as a hedge instrument in a cash flow hedge are recorded in other comprehensive income or loss. Amounts in other comprehensive income or loss are reclassified to earnings when the hedged transaction affects earnings and are classified in a manner consistent with the transaction being hedged. The Company formally documents the relationships between hedging instruments and the respective hedged items, as well as its risk management objectives for hedge transactions. The Company evaluates the effectiveness of its hedging relationships both at the hedge's inception and on an ongoing basis. Any ineffective portion of the change in fair value of a derivative instrument used as a hedge instrument in a fair value or cash flow hedge is recognized immediately in earnings. The ineffective portion is based on the extent to which exact offset is not achieved between the change in fair value of the hedge instrument and the cumulative change in expected future cash flows on the hedged transaction from inception of the hedge in a cash flow hedge or the change in the fair value. Ineffectiveness was insignificant for the years ended December 31, 2012, 2011 and 2010. See Note 9, "Derivatives" for further disclosures related to the Company's derivative instruments. Fair Value Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly hypothetical transaction between market participants at a given measurement date. Valuation techniques used must maximize the use of observable inputs and minimize the use of unobservable inputs. See Note 11, "Fair Values Measurements" for further disclosures related to the Company's recurring fair value estimates. Income Taxes Deferred income taxes are provided for temporary differences arising from differences between the financial statement amount and tax basis of assets and liabilities existing at each balance sheet date using enacted tax rates anticipated to be in effect when the related taxes are expected to be paid or recovered. A valuation allowance is established if it is more likely than not that a deferred tax asset will not be realized. In determining the need for a valuation allowance, the Company considers projected realization of tax benefits based on expected levels of future taxable income, available tax planning strategies and and the reversal of temporary differences. The benefit from tax positions that are uncertain is not recognized unless the Company concludes that it is more likely than not that the position would sustain in a dispute with taxing authorities, should the dispute be taken to the court of last resort. The Company would measure any such benefit at the largest amount of benefit that is greater than 50 percent likely of being realized upon settlement with taxing authorities. See Note 13, "Taxes" for further disclosures about income taxes. Benefit Plans The Company has non-contributory defined benefit pension plans covering most of its salaried and hourly employees. Benefits are generally based on the employee's age and compensation. The Company also currently provides certain postretirement medical and life insurance coverage for eligible employees. The cost of providing these benefits are determined on an actuarial basis and accrued over the employee's period of active service. The Company recognizes the overfunded or underfunded status of these plans as determined on an actuarial basis on the balance sheet and the changes in the funded status are recognized in other comprehensive income. See Note 18, "Employee Benefit Plans" for additional disclosures relating to these obligations. Stock-Based Compensation The compensation cost of all stock-based awards is determined based on the grant-date fair value of the award, and is recognized over the requisite service period. The grant-date fair value of option awards is determined using a Black-Scholes option pricing model. Compensation cost for an award with performance conditions is accrued if it is probable that the conditions will be met. See further discussion in Note 16, "Stock Based Compensation and Other Incentive Plans."

Debt

12 Months Ended

Dec. 31, 2012

Debt Disclosure [Abstract]

Debt

Debt and Financing Arrangements



	December 31, 2012		December 31, 2011
	(In thousands)
Indebtedness to banks under credit facilities	$	—	$	481,300
Term loan ($1.65 billion face value) due 2018	1,627,384		—
6.75% senior notes ($450.0 million face value) due 2013	—		450,971
8.75% senior notes ($600.0 million face value) due 2016	590,999		588,974
7.00% senior notes due 2019 at par	1,000,000		1,000,000
9.875% senior notes ($375.0 million face value) due 2019	360,042		—
7.25% senior notes due 2020 at par	500,000		500,000
7.25% senior notes due 2021 at par	1,000,000		1,000,000
Other	40,350		21,903
	5,118,775		4,043,148
Less current maturities of debt and short-term borrowings	32,896		280,851
Long-term debt	$	5,085,879	$	3,762,297

The current maturities of debt include contractual maturities and amounts borrowed under our revolving credit facility and accounts receivable securitization program that the Company does not intend to refinance on a long-term basis, based on cash projections and management’s plans.

On May 16, 2012, the Company entered into an amendment to its senior secured revolving credit facility that amended certain financial maintenance covenants, suspending the Company’s compliance with the debt-to-EBITDA ratio, easing other financial covenants through September 2014 and adding defined minimum EBITDA targets. The maximum borrowing capacity of the revolving credit facility was reduced from $2 billion to $600 million. In conjunction with the amendment, the Company borrowed $1.4 billion under a six-year secured term loan facility, issued at a 1% discount. The term loan contains no financial maintenance covenants, is prepayable and is secured by the same assets as borrowings under the revolving credit facility. The amendment reduced the quarterly dividend the Company may pay on its common stock to $0.03 per share.

Quarterly principal payments of $3.5 million began in September 2012, plus interest at a rate of the greater of a LIBOR-based rate or 1.25%, plus 450 basis points. The proceeds of the term loan were used to retire all outstanding borrowings under the revolving credit facility and the outstanding $450.0 million principal amount of 6.75% Senior Notes due 2013 issued by Arch Western Finance, LLC (“Arch Western Finance”), the Company’s indirect subsidiary.

On May 16, 2012, Arch Western Finance accepted for purchase an aggregate of approximately $304.0 million principal amount of its 6.75% Senior Notes due 2013 in an initial settlement pursuant to the terms of its tender offer and consent solicitation, which commenced on May 1, 2012, and called for redemption all of the remaining notes outstanding after the completion of the tender offer. The consideration for each $1,000 of principal purchased under the tender offer and consent solicitation was $1,002.50, for a total purchase consideration of $304.8 million. On May 30, 2012, the remaining notes with an outstanding principal amount of $146.0 million were redeemed at par value.

On November 21, 2012, the Company issued $375.0 million aggregate principal amount of 9.875% senior unsecured notes due 2019 (the “9.875 % Notes”) at an issue price of 95.934% of the face amount. Also on November 21, 2012, the Company borrowed an incremental $250.0 million on the term loan facility at a 1% discount at the same rate as the initial borrowing discussed previously. The principal payments on the loan increased to $4.125 million per quarter as a result of the incremental borrowing. Under the terms of the credit agreement, the incremental term loan reduced the size of Arch’s revolving credit facility to $350 million from $600 million.

At the same time, the Company amended its senior secured revolving credit facility to relax financial maintenance covenants and eliminate the minimum EBITDA targets until December 31, 2015.

The Company wrote off $23.4 million of deferred financing costs relating to the reduction in capacity of the senior secured revolving credit facility and $1.1 million related to the redemption of the 6.75% Senior Notes due 2013, offset by $(0.8) million of unamortized issue premium on the notes. The write-off of deferred financing fees, along with other transaction fees associated with these transactions, is reflected in “Loss on extinguishment and refinancing of debt” in the consolidated statements of operations.

The Company paid financing costs of $50.6 million, $114.8 million and $12.8 million in conjunction with its financing activities during the years ended December 31, 2012, 2011 and 2010, respectively. The Company's financing fees are generally deferred, however, the Company incurred a fee of $49.5 million in 2011 in conjunction with the acquisition of ICG that was expensed, as the related bridge financing facility was not used.

Credit Facilities

Borrowings under the Company's senior secured revolving credit facility bear interest at a floating rate based on LIBOR determined by reference to the Company's leverage ratio, as calculated in accordance with the underlying credit agreement. The credit facility has a five-year term that expires on June 14, 2016 and is secured by substantially all of the Company's assets as well as its ownership interests in substantially all of its subsidiaries. Commitment fees of 0.50% to 0.75% per annum are payable on the average unused daily balance of the revolving credit facility.

The Company maintains an accounts receivable securitization program under which eligible trade receivables are sold, without recourse, to a multi‑seller, asset‑backed commercial paper conduit. The entity through which these receivables are sold is consolidated into the Company's financial statements. The Company may borrow and draw letters of credit against the facility, and pays facility fees, program fees and letter of credit fees (based on amounts of outstanding letters of credit). The total aggregate borrowings and letters of credit are limited by eligible accounts receivable, as defined under the terms of the agreement. The credit facility supporting the borrowings under the program is subject to renewal annually, and expires on December 10, 2013.

Financial covenant requirements may restrict the amount of unused capacity available to the Company for borrowings and letters of credit.

On June 14, 2011, the Company terminated its commercial paper placement program and the supporting credit facility.

Since May, when borrowings under the revolving credit facility were retired with the proceeds of the term loan, we have borrowed only under the accounts receivable securitization program. At December 31, 2012, the available borrowing capacity under our lines of credit with financial institutions was approximately $333 million.

2016 Senior Notes

The Company has outstanding $600.0 million in aggregate principal amount of 8.75% senior unsecured notes due 2016 (“2016 Notes”). The 2016 Notes were issued at an initial issue price of 97.464% of the face amount. Interest is payable on the notes on February 1 and August 1 of each year. At any time on or after August 1, 2013, the Company may redeem some or all of the notes. The redemption price, reflected as a percentage of the principal amount, is: 104.375% for notes redeemed between August 1, 2013 and July 31, 2014; 102.188% for notes redeemed between August 1, 2014 and July 31, 2015; and 100% for notes redeemed on or after August 1, 2015.

2020 Senior Notes

On August 9, 2010, the Company issued $500.0 million in aggregate principal amount of 7.25% senior unsecured notes due in 2020 (“2020 Notes”) at par. Interest is payable on the 2020 Notes on April 1 and October 1 of each year. At any time on or after October 1, 2015, the Company may redeem some or all of the notes. The redemption price reflected as a percentage of the principal amount is: 103.625% for notes redeemed between October 1, 2015 and September 30, 2016; 102.417% for notes redeemed between October 1, 2016 and September 30, 2017; 101.208% for notes redeemed between October 1, 2017 and September 30, 2018; and 100% for notes redeemed on or after October 1, 2018. In addition, at any time and on one or more occasions prior to October 1, 2013, the Company may redeem an aggregate principal amount of senior notes not to exceed 35% of the original aggregate principal amount of the senior notes outstanding with the proceeds of one or more public equity offerings, at a redemption price equal to 107.250%.

2019 and 2021 Senior Notes

On June 14, 2011, the Company issued $1.0 billion of 7.00% unsecured senior notes due 2019 (“2019 Notes”) and $1.0 billion of 7.25% unsecured senior notes due 2021 (“2021 Notes”) at their face amount. These notes were used to finance, along with an issuance of common stock discussed in Note 15, "Capital Stock", the acquisition of ICG. Interest is payable on the 2019 Notes and 2021 Notes on June 15 and December 15 of each year.

At any time prior to June 15, 2014, the Company may redeem up to 35% of the original aggregate principal amount of each of the 2019 Notes and 2021 Notes, plus accrued and unpaid interest, with the net proceeds from certain equity offerings, at a redemption price, reflected as a percentage of the principal amount, equal to 107.0% and 107.25%, respectively. The Company may redeem the 2019 Notes prior to June 15, 2015 and the 2021 Notes prior to June 15, 2016 at the respective make-whole prices set forth in the indenture. On or after June 15, 2015, the Company may redeem the 2019 Notes at redemption prices, reflected as a percentage of the principal amount, of: 103.5% from June 15, 2015 through June 14, 2016; 101.75% from June 15, 2016 through June 14, 2017; and 100% beginning on June 15, 2017. On or after June 15, 2016, the Company may redeem the 2021 Notes at redemption prices, reflected as a percentage of the principal amount, of: 103.625% from June 15, 2016 through June 14, 2017; 102.417% from June 15, 2017 through June 14, 2018; 101.208% from June 15, 2018 through June 14, 2019 and 100% beginning on June 15, 2019. In each case, accrued and unpaid interest at the redemption date is due upon redemption.

9.875% Notes

Interest is payable on the 9.875%9.875% Notes annually on June 15 and December 15, beginning on June 15, 2013. At any time on or after December 15, 2016, the Company may redeem some or all of the notes. The redemption price, reflected as a percentage of the principal amount, is: 104.938% for notes redeemed between December 15, 2016 and December 14, 2017; 102.469% for notes redeemed between December 15, 2017 and December 14, 2018; and 100% for notes redeemed on or after December 15, 2018. In addition, at any time and on one or more occasions prior to December 15, 2015, the Company may redeem an aggregate principal amount of senior notes not to exceed 35% of the original aggregate principal amount of the senior notes outstanding with the proceeds of one or more public equity offerings, at a redemption price equal to 109.875%.

The unsecured senior notes are guaranteed by substantially all of the Company's subsidiaries, except for Arch Receivable Company, LLC, which is the conduit for the accounts receivable securitization program, and the Company's subsidiaries outside the U.S.

Debt Retirements

Upon the closing of the ICG acquisition, the Company gave a 30-day redemption notice to the Trustee of ICG's 9.125% senior notes and legally discharged its obligation under the 9.125% senior notes by depositing the required funds with the Trustee to redeem the debt. On July 14, 2011, all of the outstanding 9.125% senior notes were redeemed at an aggregate price of $251.4 million, including the required make-whole premium, plus accrued interest of $5.2 million.

At the acquisition date, ICG's 4.00% convertible senior notes with a fair value of $298.5 million and 9.00% convertible senior notes with a fair value of $1.7 million (“convertible notes”) became convertible into cash, pursuant to the amended indentures governing the convertible notes, at a calculated conversion rate of $2,614.6848 for each $1,000 in principal amount surrendered for conversion for the 4.00% convertible notes and $2,392.73414 for the 9.00% convertible notes for conversions occurring prior to August 17, 2011.

At the acquisition date, other ICG debt had a fair value of approximately $54.0 million and consisted mainly of equipment notes and insurance notes payable.

The Company recognized a net loss of $2.0 million during the year ended December 31, 2011 on the early extinguishment of ICG's debt, including the conversions of the 4.00% and 9.00% convertible notes described above. Any remaining amounts outstanding under the convertible notes and other ICG debt is included in “other” in the debt table above.

The Company redeemed $500.0 million aggregate principal amount of the 6.75% Senior Notes due 2013 on September 8, 2010. The Company recognized a loss on the redemption of $6.8 million, including the payment of the $5.6 million redemption premium and the write-off of $3.3 million of unamortized debt financing costs, partially offset by the write-off of $2.1 million of the original issue premium.

Debt Maturities

Expected aggregate maturities of debt for the next five years are $34.7 million in 2013, $20.6 million in 2014, $20.8 million in 2015, $620.9 million in 2016 and $21.1 million in 2017.

Terms of the Company's credit facilities and leases contain financial and other covenants that limit the ability of the Company to, among other things, acquire, dispose, merge or consolidate assets; incur additional debt; pay dividends and make distributions or repurchase stock; make investments; create liens; issue and sell capital stock of subsidiaries; enter into restrictions affecting the ability of restricted subsidiaries to make distributions, loans or advances to the Company; engage in transactions with affiliates and enter into sale and leaseback transactions. In addition, the covenants require the Company to pledge assets to collateralize the revolving credit and term loan facilities. The assets pledged include equity interests in wholly‑owned subsidiaries, certain real property interests, accounts receivable and inventory of the Company. Failure by the Company to comply with such covenants could result in an event of default, which, if not cured or waived, could have a material adverse effect on the Company.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References + Details

Mine Closure and Asset Impairment Costs

12 Months Ended

Dec. 31, 2012

Restructuring and Related Activities [Abstract]

Restructuring and Related Activities Disclosure [Text Block]

Mine Closure and Asset Impairment Costs

In response to decreasing demand for thermal coal, the Company made the decision in the second quarter of 2012 to close four thermal coal mining complexes and to temporarily idle a fifth complex, all acquired with ICG. The company also curtailed production at other Appalachia mines. These actions resulted in a total workforce reduction of approximately 750 positions. The Company will incur customary annual maintenance costs related to these properties in the future. The terms of customer contracts will be fulfilled by other operations.

The following costs are reflected in the line “Mine closure and asset impairment costs” on the consolidated statements of operations for the year ended December 31, 2012:



Parts and supplies inventory writedown	$	2,598
Impairment of property, plant and equipment	95,641
Impairment of coal properties and deferred development costs	403,279
Royalty obligations	11,546
Employee termination benefits	12,274
Pension, postretirement and occupational disease curtailment gain, net (see notes 17 and 18)	(1,770		)
	$	523,568

The Company determined that assets of the closed operations with a net book value of $51 million could be redeployed to other operations. The remainder of the assets were determined to be completely impaired, based on an analysis of the marketability of thermal coal properties in the current market environment.

The majority of the employee termination benefits were paid in the third quarter of 2012. The royalty obligations represent minimum payments on various leases and will be paid over the remaining term of the leases, through 2016.

The $7.3 million in asset impairment costs for the year ended December 31, 2011 related to a preparation plant and loadout of an acquired ICG mining operation that would not be used in ongoing operations.

- Definition

The entire disclosure for restructuring and related activities. Description of restructuring activities such as exit and disposal activities, include facts and circumstances leading to the plan, the expected plan completion date, the major types of costs associated with the plan activities, total expected costs, the accrual balance at the end of the period, and the periods over which the remaining accrual will be settled.

+ References + Details

Acquired Sales Contracts

12 Months Ended

Dec. 31, 2012

Acquired Sales Contracts [Abstract]

aci_DescriptionAcquiredSalesContractsTextBlock [Text Block]

Acquired Sales Contracts

The acquired sales contracts reflected in the consolidated balance sheets are as follows:



	December 31, 2012						December 31, 2011
	Assets			Liabilities			Assets			Liabilities
	(In thousands)						(In thousands)
Acquired fair value	$	131,819		$	166,697		$	149,457		$	166,697
Accumulated amortization	(123,776		)	(105,237		)	(115,322		)	(69,699		)
Total	$	8,043		$	61,460		$	34,135		$	96,998
Net total				$	(53,417	)				$	(62,863	)
Balance Sheet classification:
Other current	$	5,651		$	14,038		$	18,929		$	38,441
Other noncurrent	$	2,392		$	47,422		$	15,206		$	58,557

In 2012 the Company recognized an impairment loss of $15.7 million to write off a contract acquired with the ICG acquisition with an original acquired fair value of $17.5 million.

The Company anticipates amortization of acquired sales contracts, based upon expected shipments in the next five years, to be income of approximately $8.1 million in 2013, $11.6 million in 2014, $10.8 million in 2015, $9.3 million in 2016 and $3.2 million in 2017.

Accumulated Other Comprehensive Income (Loss)

12 Months Ended

Dec. 31, 2012

Accumulated Other Comprehensive Income (Loss) [Abstract]

Comprehensive Income (Loss) Note [Text Block]

Accumulated Other Comprehensive Income (Loss)

Other comprehensive income (loss) includes transactions recorded in stockholders' equity during the year, excluding net income and transactions with stockholders. Following are the items included in accumulated other comprehensive income (loss):



				Pension,
				Postretirement
				and Other						Accumulated
				Post-						Other
	Derivative			Employment			Available-for-			Comprehensive
	Instruments			Benefits			Sale Securities			Loss
	(In thousands)
Balance at January 1, 2010	$	1,186		$	(20,539	)	$	(500	)	$	(19,853	)
2010 activity, before tax	2,711			15,406			2,877			20,994
2010 activity, tax effect	(976		)	(5,546		)	(1,036		)	(7,558		)
Balance at December 31, 2010	2,921			(10,679		)	1,341			(6,417		)
2011 activity, before tax	(11,951		)	9,345			176			(2,430		)
2011 activity, tax effect	4,301			(3,342		)	(62		)	897
Balance at December 31, 2011	(4,729		)	(4,676		)	1,455			(7,950		)
2012 activity, before tax	10,895			(21,265		)	(3,000		)	(13,370		)
2012 activity, tax effect	(3,922		)	7,655			1,080			4,813
Balance at December 31, 2012	$	2,244		$	(18,286	)	$	(465	)	$	(16,507	)

- Definition

The entire disclosure for comprehensive income, which includes, but is not limited to, 1) the amount of income tax expense or benefit allocated to each component of other comprehensive income, including reclassification adjustments, 2) the reclassification adjustments for each classification of other comprehensive income and 3) the ending accumulated balances for each component of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=20435746&loc=d3e689-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.3-04)
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Reclassification Adjustments
-URI http://asc.fasb.org/extlink&oid=6522872

Reference 9: http://www.xbrl.org/2003/role/presentationRef
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-URI http://asc.fasb.org/extlink&oid=20435746&loc=d3e681-108580

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 14-26
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Investments in Available-for-Sale Securities

12 Months Ended

Dec. 31, 2012

Available-for-sale Securities [Abstract]

Available-for-sale Securities [Text Block]

. Investments in Available-for-Sale Securities

The Company has invested in marketable debt securities, primarily highly liquid AA - rated corporate bonds, U.S. government and government agency securities. These investments are held in the custody of a major financial institution. These securities, along with the Company's investments in marketable equity securities, are classified as available-for-sale securities and, accordingly, the unrealized gains and losses are recorded through other comprehensive income.

The Company's investments in available-for-sale marketable securities are as follows:



December 31, 2012										Balance Sheet
			Gross		Gross					Classification
			Unrealized		Unrealized			Fair		Short-Term		Other
	Cost Basis		Gains		Losses			Value		Investments		Assets
	(In thousands)
Available-for-sale:
U.S. government and agency securities	$	146,993	$	2	$	(412	)	$	146,583	$	146,583	$	—
Corporate notes and bonds	88,118		—		(396		)	87,722		87,722		—
Equity securities	5,271		2,704		(2,628		)	5,347		—		5,347
Total Investments	$	240,382	$	2,706	$	(3,436	)	$	239,652	$	234,305	$	5,347

The aggregate fair value of investments with unrealized losses was $223.3 million at December 31, 2012.



December 31, 2011										Balance Sheet
			Gross		Gross					Classification
			Unrealized		Unrealized			Fair		Short-Term
	Cost Basis		Gains		Losses			Value		Investments		Other Assets
	(In thousands)
Available-for-sale:
Equity securities	$	5,268	$	4,394	$	(2,122	)	$	7,540	$	—	$	7,540
Total Investments	$	5,268	$	4,394	$	(2,122	)	$	7,540	$	—	$	7,540

The debt securities outstanding at December 31, 2012 have maturity dates ranging from the first quarter of 2013 through the second quarter of 2014. The Company classifies its investments as current based on the nature of the investments and their availability for use in current operations.

- Definition

The entire disclosure for investments in certain debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Glossary Debt Security
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 3, 19, 20, 21, 22, 137
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Goodwill

12 Months Ended

Dec. 31, 2012

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill

Changes in the carrying value of goodwill for the years ended December 31, 2012, 2011 and 2010 are as follows:



	(In thousands)
Balance at January 1, 2010	$	113,701
Consideration paid related to prior business acquisitions	1,262
Balance at December 31, 2010	114,963
Consideration paid related to prior business acquisitions	829
Acquisition of ICG	480,311
Balance at December 31, 2011	596,103
Impairment	(330,680		)
Balance at December 31, 2012	$	265,423

During the second quarter of 2012, a significant drop in the Company’s stock price, combined with continuing weak demand for thermal coal during the quarter and the Company’s resulting production cuts, indicated that the fair value of the Company’s goodwill could be less than its carrying value. Accordingly, the Company performed the first step of the two-step goodwill impairment test as of June 30, 2012. The value of the Company’s Black Thunder reporting unit in the Powder River Basin, where $115.8 million of goodwill had been allocated, is sensitive to market demand for thermal coal. The further weakening in thermal coal markets had significantly impacted the projected demand for and pricing of coal produced at Black Thunder. In step one of the goodwill impairment testing, the fair value of the Black Thunder reporting unit did not exceed its carrying value, primarily due to the impact of lower demand on near term sales volumes and pricing. Based on initial estimates of the fair values of the assets and liabilities and the deficit of the fair value when compared to the related book values, the Company recorded a preliminary impairment charge for the entire $115.8 million carrying value of Black Thunder's goodwill during the second quarter of 2012. We subsequently performed a valuation of Black Thunder's assets and liabilities to determine the fair value of the reporting unit's goodwill, which supported the estimation that the goodwill allocated to the Black Thunder reporting unit had no value.

The goodwill amounts allocated to certain reporting units in the Company’s Appalachia segment acquired with the ICG acquisition are sensitive to volatility in the demand for metallurgical coal. During the 2012, metallurgical prices fell substantially from the peaks reached during 2011, when the reporting units were acquired with the Company's purchase of ICG. This caused the fair value of two of these reporting units to fall below their carrying value. The allocated goodwill of $214.9 million for those reporting units was determined to be fully impaired, based on the discounted cash flows used in the ICG acquisition valuation, adjusted for current market conditions and estimates of production levels. The Company recognized the impairment charge in the fourth quarter of 2012.

Equity Investments And Membership Interests In Joint Ventures

12 Months Ended

Dec. 31, 2012

Equity Method Investments and Joint Ventures [Abstract]

Equity Investments and Membership Interests in Joint Ventures

Below are the equity method investments reflected in the consolidated balance sheets:



	Knight Hawk			DKRW			DTA			Tenaska			Millennium			Tongue River		Total
	(In thousands)
Balance at January 1, 2010	$	49,603		$	23,589		$	14,076		$	—		$	—		$	—	$	87,268
Investments in affiliates	77,637			—			—			9,768			—			—		87,405
Advances to (distributions from) affiliates, net	(12,639		)	—			4,264			—			—			—		(8,375		)
Equity in comprehensive income (loss)	16,649			(1,628		)	(3,868		)	—			—			—		11,153
Balance at December 31, 2010	$	131,250		$	21,961		$	14,472		$	9,768		$	—		$	—	$	177,451
Investments in affiliates	—			—			—			5,500			25,000			12,989		43,489
Advances to (distributions from) affiliates, net	(16,621		)	—			6,498			—			3,477			—		(6,646		)
Equity in comprehensive income (loss)	20,596			(2,246		)	(4,884		)	(2		)	(2,153		)	—		11,311
Balance at December 31, 2011	$	135,225		$	19,715		$	16,086		$	15,266		$	26,324		$	12,989	$	225,605
Investments in affiliates	—			—			—			—			—			—		—
Advances to (distributions from) affiliates, net	(7,151		)	—			4,335			—			8,798			1,708		7,690
Equity in comprehensive income (loss)	20,989			(4,200		)	(4,959		)	(2		)	(2,908		)	—		8,920
Balance at December 31, 2012	$	149,063		$	15,515		$	15,462		$	15,264		$	32,214		$	14,697	$	242,215
Notes receivable from investees:
Balance at December 31, 2011	$	—		$	30,751		$	—		$	5,059		$	—		$	—	$	35,810
Balance at December 31, 2012	$	—		$	38,680		$	—		$	5,148		$	—		$	—	$	43,828

The Company holds an equity interest in Knight Hawk Holdings, LLC ("Knight Hawk"), a coal producer in the Illinois Basin. In June 2010, the Company exchanged 68.4 million tons of coal reserves in the Illinois Basin for an additional 9% ownership interest, increasing the Company's ownership in Knight Hawk to 42% from 33.33%. The Company recognized a gain of $41.6 million on the transaction, representing the difference between the fair value and the $12.1 million net book value of the coal reserves, adjusted for the Company's retained ownership interest in the reserves through its investment in Knight Hawk. In December 2010, the Company increased its ownership interest in Knight Hawk to 49% for $26.6 million in cash.

The Company holds a 24% equity interest in DKRW Advanced Fuels LLC ("DKRW"), a company engaged in developing coal-to-liquids facilities. DKRW may borrow funds from the Company under a convertible secured promissory note. Amounts borrowed are due and payable in cash or in additional equity interests on the earlier of June 30, 2013 or upon the closing of DKRW's next financing, bear interest at the rate of 15% per annum, and are secured by DKRW's equity interests in Medicine Bow Fuel & Power LLC. The note balances above are reflected in other receivables on the consolidated balance sheets.

The Company holds a general partnership interest of 21.875% in Dominion Terminal Associates ("DTA"), which is accounted for under the equity method. DTA operates a ground storage-to-vessel coal transloading facility in Newport News, Virginia for use by the partners. Under the terms of a throughput and handling agreement with DTA, each partner is charged its share of cash operating and debt-service costs in exchange for the right to use the facility's loading capacity and is required to make periodic cash advances to DTA to fund such costs.

The Company holds a 35% ownership interest in Tenaska Trailblazer Partners, LLC ("Tenaska"), the developer of the Trailblazer Energy Center, a fossil-fuel-based electric power plant near Sweetwater, Texas. The plant, fueled by low sulfur coal, will capture and store carbon dioxide for enhanced oil recovery applications. Additional future payments are due upon the achievement of project milestones to maintain the Company's interest. The Company made a milestone payment of $5.5 million in 2011. The Company will also pay 35% of the future development costs of the project, not to exceed $12.5 million without prior approval from the Company. The receivables for these development costs, shown above, are reflected in the consolidated balance sheets in other noncurrent assets, as the development costs will either be reimbursed when the project receives construction financing, or they will be considered an additional capital contribution, with ownership percentages adjusted accordingly.

In January 2011, the Company purchased a 38% ownership interest in Millennium Bulk Terminals-Longview, LLC ("Millennium"), the owner of a brownfield bulk commodity terminal on the Columbia River near Longview, Washington, for $25.0 million, plus additional future consideration upon the completion of certain project milestones. Millennium continues to work on obtaining the required approvals and necessary permits to complete dredging and other upgrades to enable coal, alumina and cementitious material shipments through the terminal. The Company will control 38% of the terminal's throughput and storage capacity, in order to facilitate export shipments of coal off the west coast of the United States.

In July 2011, the Company purchased a 35% membership interest in the Tongue River Holding Company, LLC ("Tongue River") joint venture. Tongue River will develop and construct a railway line near Miles City, Montana and the Company's Otter Creek reserves. The Company has the right, upon the receipt of permits and approval for construction or under other prescribed circumstances, to require the other investors to purchase all of the Company's units in the venture at an amount equal to the capital contributions made by the Company at that time, less any distributions received.

The Company may be required to make future contingent payments of up to $72.9 million related to development financing for certain of its equity investees. The Company’s obligation to make these payments, as well as the timing of any payments required, is contingent upon a number of factors, including project development progress, receipt of permits and construction financing.

Summarized financial information of the Company's equity method investees follows:



	December 31
	2012		2011		2010
	(In thousands)
Condensed combined income statement information:
Revenues	$	190,661	$	184,358	$	172,933
Gross profit	15,308		19,495		25,203
Income from operations	8,898		13,180		20,243
Net income	641		6,788		16,015
Condensed combined balance sheet information:
Current assets	$	78,961	$	94,644
Noncurrent assets	387,884		331,848
Total assets	$	466,845	$	426,492
Current liabilities	$	57,403	$	51,674
Noncurrent liabilities	128,489		120,494
Equity	280,690		254,163
Noncontrolling interest	263		161
Total liabilities and equity	$	466,845	$	426,492

- Definition

The entire disclosure for equity method investments and joint ventures. Equity method investments are investments that give the investor the ability to exercise significant influence over the operating and financial policies of an investee. Joint ventures are entities owned and operated by a small group of businesses as a separate and specific business or project for the mutual benefit of the members of the group.

+ References + Details

Derivatives

12 Months Ended

Dec. 31, 2012

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivatives

Diesel fuel price risk management

The Company is exposed to price risk with respect to diesel fuel purchased for use in its operations. The Company anticipates purchasing approximately 57 to 67 million gallons of diesel fuel for use in its operations during 2013. To protect the Company’s cash flows from increases in the price of diesel fuel for its operations, the Company uses forward physical diesel purchase contracts and purchased heating oil call options, and in the past, heating oil swaps. At December 31, 2012, the Company had protected the price of substantially all of its 2013 purchases. At December 31, 2012, the Company had purchased heating oil call options for approximately 60 million gallons for the purpose of managing the price risk associated with future diesel purchases.

The Company also purchased heating oil call options to hedge the fuel surcharges on its barge and rail shipments that cover increases in diesel fuel prices. These positions reduce the Company’s risk of cash flow fluctuations related to these surcharges but the positions are not accounted for as hedges. At December 31, 2012, the Company held purchased call options for approximately 15 million gallons for the purpose of managing the fluctuations in cash flows associated with fuel surcharges on future shipments.

Coal risk management positions

The Company may sell or purchase forward contracts, swaps and options in the over-the-counter coal market in order to manage its exposure to coal prices. The Company has exposure to the risk of fluctuating coal prices related to forecasted sales or purchases of coal or to the risk of changes in the fair value of a fixed price physical sales contract. Certain derivative contracts may be designated as hedges of these risks.

At December 31, 2012, the Company held derivatives for risk management purposes that are expected to settle in the following years:



(Tons in thousands)	2013	2014	2015	Total
Coal sales	6,704	4,260	780	11,744
Coal purchases	1,410	1,260	—	2,670

Coal trading positions

The Company may sell or purchase forward contracts, swaps and options in the over-the-counter coal market for trading purposes. The Company is exposed to the risk of changes in coal prices on the value of its coal trading portfolio. The estimated future realization of the value of the trading portfolio is $1.1 million of losses in 2013 and $1.5 million of gains in 2014.

Tabular derivatives disclosures

The Company’s contracts with certain of its counterparties allow for the settlement of contracts in an asset position with contracts in a liability position in the event of default or termination. Such netting arrangements reduce the Company’s credit exposure related to these counterparties. For classification purposes, the Company records the net fair value of all the positions with a given counterparty as a net asset or liability in the consolidated balance sheets. The amounts shown in the table below represent the fair value position of individual contracts, and not the net position presented in the accompanying consolidated balance sheets. The fair value and location of derivatives reflected in the accompanying consolidated balance sheets are as follows:



	December 31, 2012								December 31, 2011
Fair Value of Derivatives	Asset			Liability					Asset			Liability
(In thousands)	Derivative			Derivative					Derivative			Derivative
Derivatives Designated as Hedging Instruments
Heating oil--diesel purchases	$	—		$	—				$	8,997		$	—
Coal	3,277			(10		)			1,109			—
Total	3,277			(10		)			10,106			—
Derivatives Not Designated as Hedging Instruments
Heating oil -- diesel purchases	7,379			—					—			—
Heating oil -- fuel surcharges	1,961			—					1,797			—
Coal -- held for trading purposes	17,403			(16,933		)			15,505			(19,927		)
Coal -- risk management	24,843			(7,342		)			14,855			(6,035		)
Total	51,586			(24,275		)			32,157			(25,962		)
Total derivatives	54,863			(24,285		)			42,263			(25,962		)
Effect of counterparty netting	(22,548		)	22,548					(18,134		)	18,134
Net derivatives as classified in the balance sheets	$	32,315		$	(1,737	)	$	30,578	$	24,129		$	(7,828	)	$	16,301



		December 31, 2012			December 31, 2011
Net derivatives as reflected on the balance sheets
Heating oil	Other current assets	$	9,340		$	10,794
Coal	Coal derivative assets	22,975			13,335
	Coal derivative liabilities	(1,737		)	(7,828		)
		$	30,578		$	16,301

The Company had a current asset for the right to reclaim cash collateral of $16.2 million and $12.4 million at December 31, 2012 and December 31, 2011, respectively. These amounts are not included with the derivatives presented in the table above and are included in “other current assets” in the accompanying consolidated balance sheets.

During the first quarter of 2012, the Company determined the effectiveness of the heating oil options could not be established as of December 31, 2011 and on an ongoing basis. As a result, the amount remaining in accumulated other comprehensive income of $8.2 million was recorded in the “other operating income, net” line on the consolidated statement of operations, or $5.2 million net of income taxes.

The effects of derivatives on measures of financial performance are as follows:

Derivatives used in Cash Flow Hedging Relationships (in thousands)

For the year ended December 31,



		Gain (Loss) Recognized in Other Comprehensive Income(Effective Portion)									Gains (Losses) Reclassified from Other Comprehensive Income into Income (Effective Portion)
	⁽²⁾	2012			2011			2010			2012		2011		2010
Heating oil — diesel purchases	⁽¹⁾	$	—		$	1,294		$	(149	)	$	—	$	14,866	$	437
Coal sales	⁽²⁾	7,690			4,923			(4,714		)	2,675		1,572		(1,602		)
Coal purchases		(2,440		)	(2,009		)	5,145			—		—		(1,202		)
Totals		$	5,250		$	4,208		$	282		$	2,675	$	16,438	$	(2,367	)

No ineffectiveness or amounts excluded from effectiveness testing relating to the Company’s cash flow hedging relationships were recognized in the results of operations in the twelve month periods ended December 31, 2012 and 2011.

Derivatives Not Designated as Hedging Instruments (in thousands)

For the year ended December 31



		Gain (Loss) Recognized
		2012			2011			2010
Coal — unrealized	⁽³⁾	$	8,272		$	6,438		$	(10,991	)
Coal — realized	⁽⁴⁾	$	43,990		$	(7	)	$	4,542
Heating oil — diesel purchases	⁽⁴⁾	$	(22,281	)	$	(2,906	)	$	—
Heating oil — fuel surcharges	⁽⁴⁾	$	(2,209	)	$	—		$	—

____________________________________________________________

Location in statement of operations:

(1) — Revenues

(2) — Cost of sales

(3) — Change in fair value of coal derivatives and coal trading activities, net

(4) — Other operating income, net

The Company recognized net unrealized and realized gains of $8.3 million, losses of $3.5 million, and gains of $2.1 million during the year ended December 31, 2012, 2011, and 2010, respectively, related to its trading portfolio, which are included in the caption “Change in fair value of coal derivatives and coal trading activities, net” in the accompanying consolidated statements of operations, and are not included in the previous tables reflecting the effects of derivatives on measures of financial performance.

Based on fair values at December 31, 2012, gains on derivative contracts designated as hedge instruments in cash flow hedges of approximately $2.2 million are expected to be reclassified from other comprehensive income into earnings during the next twelve months.

- Definition

The entire disclosure for the entity's entire derivative instruments and hedging activities. Describes an entity's risk management strategies, derivatives in hedging activities and non-hedging derivative instruments, the assets, obligations, liabilities, revenues and expenses arising therefrom, and the amounts of and methodologies and assumptions used in determining the amounts of such items.

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+ Details

Inventories

12 Months Ended

Dec. 31, 2012

Inventory Disclosure [Abstract]

Inventories

Inventories consist of the following:



	December 31
	2012		2011
	(In thousands)
Coal	$	180,917	$	206,517
Repair parts and supplies	172,139		163,527
Work-in-process	12,368		7,446
	$	365,424	$	377,490

The repair parts and supplies are stated net of an allowance for slow-moving and obsolete inventories of $13.6 million at December 31, 2012, and $13.1 million at December 31, 2011.

Fair Value Measurements

12 Months Ended

Dec. 31, 2012

Fair Value Disclosures [Abstract]

Fair Value Measurements

The hierarchy of fair value measurements prioritizes the inputs to valuation techniques used to measure fair value. The levels of the hierarchy, as defined below, give the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs.

· Level 1 is defined as observable inputs such as quoted prices in active markets for identical assets. Level 1 assets include available-for-sale equity securities, U.S. Treasury securities, and coal futures that are submitted for clearing on the New York Mercantile Exchange.

· Level 2 is defined as observable inputs other than Level 1 prices. These include quoted prices for similar assets or liabilities in an active market, quoted prices for identical assets and liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. The Company’s level 2 assets and liabilities include U.S. government agency securities and commodity contracts (coal and heating oil) with fair values derived from quoted prices in over-the-counter markets or from prices received from direct broker quotes.

· Level 3 is defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. These include the Company’s commodity option contracts (coal and heating oil) valued using modeling techniques, such as Black-Scholes, that require the use of inputs, particularly volatility, that are rarely observable. Changes in the unobservable inputs would not have a significant impact on the reported Level 3 fair values at December 31, 2012.

The table below sets forth, by level, the Company’s financial assets and liabilities that are recorded at fair value in the accompanying consolidated balance sheet:



	Fair Value at December 31, 2012
	Total		Level 1		Level 2		Level 3
	(In thousands)
Assets:
Investments in marketable securities	$	239,652	$	103,439	$	136,213	$	—
Derivatives	32,315		22,465		510		9,340
Total assets	$	271,967	$	125,904	$	136,723	$	9,340
Liabilities:
Derivatives	$	1,737	$	—	$	571	$	1,166

The Company’s contracts with certain of its counterparties allow for the settlement of contracts in an asset position with contracts in a liability position in the event of default or termination. For classification purposes, the Company records the net fair value of all the positions with these counterparties as a net asset or liability. Each level in the table above displays the underlying contracts according to their classification in the accompanying consolidated balance sheet, based on this counterparty netting.

The following table summarizes the change in the fair values of financial instruments categorized as level 3.



	Year Ended December 31, 2012
Balance, beginning of period	$	6,211
Realized and unrealized losses recognized in earnings, net	(13,399		)
Realized and unrealized losses recognized in other comprehensive income, net	—
Purchases	17,312
Issuances	—
Settlements	(1,950		)
Ending balance	$	8,174

Net unrealized losses during the twelve month period ended December 31, 2012 related to level 3 financial instruments held on December 31, 2012 were $5.4 million.

Fair Value of Long-Term Debt

At December 31, 2012 and December 31, 2011, the fair value of the Company’s debt, including amounts classified as current, was $5.0 billion and $4.2 billion, respectively. Fair values are based upon observed prices in an active market when available or from valuation models using market information, which fall into Level 2 in the fair value hierarchy.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References

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Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13504-108611

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13433-108611

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 15B
-Subparagraph a, b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 44A, 44B
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 159
-Paragraph 17-22, 27, 28
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 15A
-Subparagraph a-d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 15C, 15D
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 157
-Paragraph 32, 33, 34
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 3, 10, 14, 15
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2012

Accrued Expenses and Other Current Liabilities [Abstract]

Accounts Payable and Accrued Liabilities Disclosure [Text Block]

Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following:



	December 31
	2012		2011
	(In thousands)
Payroll and employee benefits	$	72,405	$	65,323
Taxes other than income taxes	121,029		133,331
Interest	42,413		55,266
Acquired sales contracts (See Note 4)	14,038		38,441
Workers’ compensation (See Note 17)	10,371		11,666
Asset retirement obligations (See Note 14)	38,920		27,119
Other	18,842		17,061
	$	318,018	$	348,207

Taxes

12 Months Ended

Dec. 31, 2012

Taxes [Abstract]

Income Tax Disclosure [Text Block]

. Taxes

The Company is subject to U.S. federal income tax as well as income tax in multiple state jurisdictions. The tax years 2006 through 2012 remain open to examination for U.S. federal income tax matters and 1998 through 2012 remain open to examination for various state income tax matters.

Significant components of the provision for (benefit from) income taxes are as follows:



	Year Ended December 31
	2012			2011			2010
	(In thousands)
Current:
Federal	$	(20,022	)	$	(20,164	)	$	34,304
State	575			1,212			2,283
Total current	(19,447		)	(18,952		)	36,587
Deferred:
Federal	(322,104		)	13,214			(18,506		)
State	7,834			(1,851		)	(367		)
Total deferred	(314,270		)	11,363			(18,873		)
	$	(333,717	)	$	(7,589	)	$	17,714

A reconciliation of the statutory federal income tax provision (benefit) at the statutory rate to the actual provision for (benefit from) income taxes follows:



	Year Ended December 31
	2012			2011			2010
	(In thousands)
Income tax provision (benefit) at statutory rate	$	(356,185	)	$	46,933		$	61,800
Percentage depletion allowance	(40,698		)	(61,971		)	(49,152		)
Goodwill	56,916			—			—
State taxes, net of effect of federal taxes	(23,423		)	(3,055		)	2,299
Change in valuation allowance	31,832			2,416			(383		)
Other, net	(2,159		)	8,088			3,150
	$	(333,717	)	$	(7,589	)	$	17,714

In 2012, 2011 and 2010, compensatory stock options and other equity based compensation awards were exercised resulting in a tax expense (benefit) of $0.3 million, $(0.4) million and $(0.8) million, respectively. The tax benefit will be recorded in paid-in capital at such point in time when a cash tax benefit is recognized.

Significant components of the Company's deferred tax assets and liabilities that result from carryforwards and temporary differences between the financial statement basis and tax basis of assets and liabilities are summarized as follows:



	December 31
	2012			2011
	(In thousands)
Deferred tax assets:
Net operating loss carryforwards	$	496,330		$	324,393
Alternative minimum tax credit carryforwards	150,014			151,404
Reclamation and mine closure	104,570			93,914
Goodwill	43,839			—
Acquired sales contracts	38,735			44,717
Workers' compensation	32,241			26,266
Retiree benefit plans	32,087			24,456
Other, primarily accrued liabilities	113,777			120,993
Gross deferred tax assets	1,011,593			786,143
Valuation allowance	(34,663		)	(2,831		)
Total deferred tax assets	976,930			783,312
Deferred tax liabilities:
Plant and equipment	1,411,446			1,566,769
Deferred development	77,013			67,728
Investment in tax partnerships	72,513			66,502
Other	12,780			17,015
Total deferred tax liabilities	1,573,752			1,718,014
Net deferred tax asset (liability)	(596,822		)	(934,702		)
Current asset (liability)	67,360			42,051
Non-current deferred tax asset (liability)	$	(664,182	)	$	(976,753	)

The Company has federal net operating loss carryforwards for regular income tax purposes of $1.3 billion at December 31, 2012 that will expire between 2024 and 2032. The Company has an alternative minimum tax credit carryforward of $150.0 million at December 31, 2012, which has no expiration date and can be used to offset future regular tax in excess of the alternative minimum tax.

During 2008, the Company reached a settlement with the IRS regarding the Company's treatment of the acquisition of the coal operations of Atlantic Richfield Company ("ARCO") and the simultaneous combination of the acquired ARCO operations and the Company's Wyoming operations into the Arch Western joint venture. The settlement did not result in a net change in deferred tax assets, but involved a re-characterization of deferred tax assets, including an increase in net operating loss carryforwards of $145.1 million and other amortizable assets which will provide additional tax deductions through 2013. A portion of these cash tax benefits accrued to ARCO pursuant to the original purchase agreement, including $0.8 million and $1.3 million paid in 2011 and 2010, respectively, that was recorded as goodwill.

The Company has recorded a valuation allowance for a portion of its deferred tax assets that management believes, more likely than not, will not be realized. Management reassesses the ability to realize its deferred tax assets annually in the fourth quarter or when circumstances indicate that the ability to realize deferred tax assets has changed. This review resulted in increases (decreases) in the valuation allowance of $31.8 million, $2.1 million and $(0.4) million in 2012, 2011 and 2010, respectively. The valuation allowance relates to certain state and foreign net operating loss benefits.

A reconciliation of the beginning and ending amounts of gross unrecognized tax benefits follows:



	(In thousands)
Balance at January 1, 2010	$	6,670
Additions based on tax positions related to the current year	1,493
Additions for tax positions of prior years	85
Reductions for tax positions of prior years	(3,830		)
Balance at December 31, 2010	4,418
Additions based on tax positions related to the current year	1,626
Additions for tax positions of prior years	2,754
Balance at December 31, 2011	8,798
Additions based on tax positions related to the current year	409
Additions for tax positions of prior years	21,943
Balance at December 31, 2012	$	31,150

If recognized, the entire amount of the gross unrecognized tax benefits at December 31, 2012 would affect the effective tax rate.

The Company recognizes interest and penalties related to unrecognized tax benefits in income tax expense. The Company had accrued interest and penalties of $1.0 million and $0.8 million at December 31, 2012 and 2011, respectively, of which $0.2 million was recognized as expense during 2012 and 2011. No gross unrecognized tax benefits are expected to be reduced in the next 12 months due to the expiration of the statute of limitations.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

+ Details

Asset Retirement Obligations

12 Months Ended

Dec. 31, 2012

Asset Retirement Obligations [Abstract]

Asset Retirement Obligation Disclosure [Text Block]

. Asset Retirement Obligations

The Company's asset retirement obligations arise from the Federal Surface Mining Control and Reclamation Act of 1977 and similar state statutes, which require that mine property be restored in accordance with specified standards and an approved reclamation plan. The required reclamation activities to be performed are outlined in the Company's mining permits. These activities include reclaiming the pit and support acreage at surface mines, sealing portals at underground mines, and reclaiming refuse areas and slurry ponds.

The following table describes the changes to the Company's asset retirement obligation liability:



	Year Ended December 31
	2012			2011
	(In thousands)
Balance at January 1 (including current portion)	$	473,903		$	343,119
Accretion expense	39,020			33,601
Obligations incurred or acquired	—			115,019
Adjustments to the liability from changes in estimates	4,400			11,176
Liabilities settled	(68,698		)	(29,012		)
Balance at December 31	$	448,625		$	473,903
Current portion included in accrued expenses	(38,920		)	(27,119		)
Noncurrent liability	$	409,705		$	446,784

The liabilities settled in 2012 were the result of the acceleration of reclamation activities, primarily at the Black Thunder mining complex, as employees and equipment impacted by mine production cutbacks in response to market conditions were redirected to reclamation activities. Liabilities settled of $29.0 million in 2011 related to reclamation activities at the Black Thunder mining complex related to a pit acquired with the Jacobs Ranch operations in 2009.

As of December 31, 2012, the Company had $262.9 million in surety bonds outstanding, $388.4 million in self-bonding, and $18.0 million in letters of credit to secure reclamation bonding obligations.

Capital Stock	12 Months Ended
Capital Stock	Dec. 31, 2012
Capital Stock [Abstract]
Capital Stock	. Capital Stock On March 1, 2012, the Company filed a registration statement on Form S-3 with the SEC. The registration statement allows the Company to offer, from time to time, an unlimited amount of debt securities, preferred stock, depositary shares, purchase contracts, purchase units, common stock and related rights and warrants. Common Stock On June 8, 2011, the Company sold 48 million shares of its common stock at a public offering price of $27.00 per share. The $1.25 billion in net proceeds from the issuance were used to finance the acquisition of ICG. On July 8, 2011, the Company issued an additional 0.7 million shares of its common stock under the same terms and conditions to cover underwriters' over-allotments for net proceeds of $18.4 million. Stock Repurchase Plan The Company's share repurchase program allows for the purchase of up to 14,000,000 shares of the Company's common stock. At December 31, 2012, 10,925,800 shares of common stock were available for repurchase under the plan. There were no purchases made under the plan during 2012, 2011 or 2010. There is no expiration date on the program. Any future repurchases under the plan will be made at management's discretion and will depend on market conditions and other factors.

- Definition

The entire disclosure for shareholders' equity, comprised of portions attributable to the parent entity and noncontrolling interest, if any, including other comprehensive income (as applicable). Including, but not limited to: (1) balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings; (2) accumulated balance for each classification of other comprehensive income and total amount of comprehensive income; (3) amount and nature of changes in separate accounts, including the number of shares authorized and outstanding, number of shares issued upon exercise and conversion, and for other comprehensive income, the adjustments for reclassifications to net income; (4) rights and privileges of each class of stock authorized; (5) basis of treasury stock, if other than cost, and amounts paid and accounting treatment for treasury stock purchased significantly in excess of market; (6) dividends paid or payable per share and in the aggregate for each class of stock for each period presented; (7) dividend restrictions and accumulated preferred dividends in arrears (in aggregate and per share amount); (8) retained earnings appropriations or restrictions, such as dividend restrictions; (9) impact of change in accounting principle, initial adoption of new accounting principle and correction of an error in previously issued financial statements; (10) shares held in trust for Employee Stock Ownership Plan (ESOP); (11) deferred compensation related to issuance of capital stock; (12) note received for issuance of stock; (13) unamortized discount on shares; (14) description, terms, and number of warrants or rights outstanding; (15) shares under subscription and subscription receivables, effective date of new retained earnings after quasi-reorganization and deficit eliminated by quasi-reorganization and, for a period of at least ten years after the effective date, the point in time from which the new retained dates; and (16) retroactive effective of subsequent change in capital structure.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 4.E)
-URI http://asc.fasb.org/extlink&oid=6228006&loc=d3e74512-122707

Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 210
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
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-Paragraph 4
-Subparagraph (SAB TOPIC 4.C)
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=6959260&loc=d3e187085-122770

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
-Section B
-Paragraph 7, 11A
-Chapter 1
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 12
-Paragraph 10
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 16: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 5
-Paragraph 15
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 17: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph d
-Article 4

Reference 18: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 29, 30, 31
-Article 5

Reference 19: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 20: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Article 4

Reference 21: http://www.xbrl.org/2003/role/presentationRef
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-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
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Reference 22: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 129
-Paragraph 2, 3, 4, 5, 6, 7, 8
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 23: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

+ Details

Stock-Based Compensation And Other Incentive Plans

12 Months Ended

Dec. 31, 2012

Share-based Compensation [Abstract]

Stock-Based Compensation And Other Incentive Plans

Stock-Based Compensation and Other Incentive Plans

Under the Company's Stock Incentive Plan (the "Incentive Plan"), 18,000,000 shares of the Company's common stock are reserved for awards to officers and other selected key management employees of the Company. The Incentive Plan provides the Board of Directors with the flexibility to grant stock options, stock appreciation rights, restricted stock awards, restricted stock units, performance stock or units, merit awards, phantom stock awards and rights to acquire stock through purchase under a stock purchase program ("Awards"). Awards the Board of Directors elects to pay out in cash do not count against the 18,000,000 shares authorized in the Incentive Plan. The Incentive Plan calls for the adjustment of shares awarded under the plan in the event of a split.

As of December 31, 2012, the Company had stock options, restricted stock and restricted stock units outstanding under the Incentive Plan.

Stock Options

Stock options are granted at a price equal to the closing market price of the Company's common stock on the date of grant and are generally subject to vesting provisions of at least one year from the date of grant. Information regarding stock option activity under the Incentive Plan follows for the year ended December 31, 2012:



			Weighted Average		Aggregate		Average
	Common		Exercise		Intrinsic		Contract
	Shares		Price		Value		Life
	(In thousands)		(In thousands)		(In thousands)
Options outstanding at January 1	4,953		$	26.72
Granted	1,311		13.28
Exercised	(527	)	9.79
Canceled	(73	)	31.17
Expired	(449	)	13.89
Options outstanding at December 31	5,215		25.99		$	4	6.67
Options exercisable at December 31	2,847		32.26		—		5.40

The aggregate intrinsic value of options exercised during the years ended December 31, 2012, 2011 and 2010 was $1.8 million, $2.6 million and $3.0 million, respectively.

Information regarding changes in stock options outstanding and not yet vested and the related grant-date fair value under the Incentive Plan follows for the year ended December 31, 2012:



		Weighted Average
	Common Shares	Grant-Date Fair Value
	(In thousands)
Unvested options at January 1	1,796	$	10.96
Granted	1,311	5.27
Vested	(721)	11.13
Canceled	(17)	9.81
Unvested options at December 31	2,369	7.77

Compensation expense related to stock options for the years ended December 31, 2012, 2011 and 2010 was $8.0 million, $8.8 million and $10.6 million, respectively. As of December 31, 2012, there was $7.0 million of unrecognized compensation cost related to the unvested stock options. The total grant-date fair value of options vested during the years ended December 31, 2012, 2011 and 2010 was $8.0 million, $9.9 million and $10.6 million, respectively. The options provide for the continuation of vesting for retirement-eligible recipients that meet certain criteria. The expense for these options is recognized through the date that the employee first becomes eligible to retire and is no longer required to provide service to earn part or all of the award. The majority of the cost relating to the stock-based compensation plans is included primarily in selling, general and administrative expenses in the accompanying consolidated statements of income.

Weighted average assumptions used in the Black-Scholes option pricing model for granted options follow:



	Year Ended December 31
	2012		2011		2010
Weighted average grant-date fair value per share of options granted	$	5.27	$	14.18	$	9.43
Assumptions (weighted average):
Risk-free interest rate	0.76%		1.92%		2.16%
Expected dividend yield	2.92%		1.25%		1.99%
Expected volatility	60.72%		57.4%		57.1%
Expected life (in years)	4.5		4.5		4.5

Expected volatilities are based on historical stock price movement and implied volatility from traded options on the Company's stock. The expected life of the option was determined based on historical exercise activity. Most options granted vest over a period of three to four years.

Restricted Stock and Restricted Stock Unit Awards

The Company may issue restricted stock and restricted stock units, which require no payment from the employee. Restricted stock cliff-vests at various dates and restricted stock units typically vest ratably over three years. Compensation expense is based on the fair value on the grant date and is recorded ratably over the vesting period. During the vesting period, the employee receives cash compensation equal to the amount of dividends that would have been paid on the underlying shares.

Information regarding restricted stock and restricted stock unit activity and weighted average grant-date fair value follows for the year ended December 31, 2012:



	Restricted Stock				Restricted Stock Units
			Weighted Average				Weighted Average
	Common		Grant-Date		Common		Grant-Date
	Shares		Fair Value		Shares		Fair Value
	(In thousands)				(In thousands)
Outstanding at January 1	182		$	26.68	27		$	52.69
Granted	22		13.44		547		13.31
Vested	(10	)	22.89		(27	)	52.69
Canceled	(6	)	32.49		(36	)	13.93
Outstanding at December 31	188		25.14		511		13.26

The weighted average fair value of restricted stock granted during 2011 and 2010 was $30.42 and $22.03, respectively. There were no restricted stock units granted during 2011 or 2010. The total grant-date fair value of restricted stock that vested during 2012, 2011 and 2010 was $0.2 million, $1.1 million and $0.4 million, respectively. The total grant-date fair value of restricted stock units that vested during 2012 and 2011 was $1.4 million in each year. There were no restricted stock units that vested during 2010.

Unearned compensation of $6.9 million will be recognized over the remaining vesting period of the outstanding restricted stock and restricted stock units. The Company recognized expense of approximately $3.5 million, $2.1 million and $1.1 million related to restricted stock and restricted stock units for the years ended December 31, 2012, 2011 and 2010, respectively, primarily in selling, general and administrative expenses.

Long-Term Incentive Compensation

The Company has a long-term incentive program that allows for the award of performance units. The total number of units earned by a participant is based on financial and operational performance measures, and may be paid out in cash or in shares of the Company's common stock. The Company recognizes compensation expense over the three year term of the grant. The liabilities are remeasured quarterly. The Company recognized $8.1 million, $2.7 million and $3.8 million for the years ended December 31, 2012, 2011 and 2010, respectively. The expense is included primarily in selling, general and administrative expenses in the accompanying consolidated statements of income. Amounts accrued under the plan were $13.1 million and $9.6 million at December 31, 2012 and 2011, respectively.

Deferred Compensation Plan

The Company maintains a deferred compensation plan that allows eligible employees to defer receipt of compensation until the dates elected by the participant. Participants in the plan may defer up to 85% of their base salaries and up to 100% of their annual incentive awards. The plan also allows participants to defer receipt of up to 100% of the shares under any restricted stock unit or performance-contingent stock awards. The amounts deferred are invested in accounts that mirror the gains and losses of a number of different investment funds, including a hypothetical investment in shares of the Company's common stock. Participants are always vested in their deferrals to the plan and any related earnings. The Company has established a grantor trust to fund the obligations under the plan. The trust has purchased corporate-owned life insurance to offset these obligations. The net cash surrender values of the policies of $35.4 million and $35.8 million at December 31, 2012 and 2011, respectively, are included in other noncurrent assets in the accompanying consolidated balance sheets. The participants have an unsecured contractual commitment by the Company to pay the amounts due under the plan. Any assets placed in trust by the Company to fund future obligations of the plan are subject to the claims of creditors in the event of insolvency or bankruptcy, and participants are general creditors of the company as to their deferred compensation in the plans.

Under the plan, the Company credits each participant's account with the number of units equal to the number of shares or units that the participant could purchase or receive with the amount of compensation deferred, based upon the fair market value of the underlying investment on that date. The amount the employee will receive from the plan will be based on the number of units credited to each participant's account, valued on the basis of the fair market value of an equivalent number of shares or units of the underlying investment on that date. The liability under the plan was $31.3 million at December 31, 2012 and $32.7 million at December 31, 2011.

The Company's net income (expense) related to the deferred compensation plan for the years ended December 31, 2012, 2011 and 2010 was $3.3 million, $6.2 million and $(2.8) million, respectively, most of which is included in selling, general and administrative expenses in the accompanying consolidated statements of income.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 50
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6406099&loc=d3e25284-112666

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5444-113901

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 14

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph 64, 65, A240
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Statement of Position (SOP)
-Number 93-6
-Paragraph 53
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Accrued Workers' Compensation

12 Months Ended

Dec. 31, 2012

Workers' Compensation Expense [Abstract]

Workers' Compensation Expense

Accrued Workers’ Compensation

The Company is liable under the Federal Mine Safety and Health Act of 1969, as subsequently amended, to provide for pneumoconiosis (occupational disease) benefits to eligible employees, former employees, and dependents. The Company is also liable under various states' statutes for occupational disease benefits. The Company currently provides for federal and state claims principally through a self-insurance program. The occupational disease benefit obligation represents the present value of the actuarially computed present and future liabilities for such benefits over the employees' applicable years of service.

In addition, the Company is liable for workers' compensation benefits for traumatic injuries that are accrued as injuries are incurred. Traumatic claims are either covered through self-insured programs or through state-sponsored workers' compensation programs.

Workers' compensation expense consists of the following components:



	Year Ended December 31
	2012			2011			2010
	(In thousands)
Self-insured occupational disease benefits:
Service cost	$	1,993		$	2,059		$	727
Interest cost	2,400			1,799			675
Net amortization	(453		)	(493		)	(1,860		)
Curtailments	3,022			—			—
Total occupational disease	6,962			3,365			(458		)
Traumatic injury claims and assessments	26,565			16,979			9,263
Total workers’ compensation expense	$	33,527		$	20,344		$	8,805

The reconciliation of changes in the benefit obligation of the occupational disease liability is as follows:



	December 31
	2012			2011
	(In thousands)
Beginning of year obligation	$	54,184		$	17,412
Service cost	1,993			2,059
Interest cost	2,400			1,799
Actuarial loss (gain)	(5,373		)	7,081
Benefit and administrative payments	(1,873		)	(1,097		)
Curtailments	7,100			—
Acquisition of ICG	—			26,930
Net obligation at end of year	$	58,431		$	54,184

At December 31, 2012 and 2011, accumulated losses of $4.7 million and $5.5 million, respectively, were not yet recognized in occupational disease cost and were recorded in accumulated other comprehensive income. The expected accumulated loss that will be amortized from accumulated other comprehensive income into occupational disease cost in 2013 is $0.9 million.

The following table provides the assumptions used to determine the projected occupational disease obligation:



	Year Ended December 31
	2012		2011		2010
Weighted average assumptions:
Discount rate	4.54	%	5.10	%	5.96	%
Cost escalation rate	3.00	%	3.00	%	3.00	%

Summarized below is information about the amounts recognized in the accompanying consolidated balance sheets for workers' compensation benefits:



	December 31
	2012		2011
	(In thousands)
Occupational disease costs	$	58,431	$	54,184
Traumatic and other workers' compensation claims	33,569		29,430
Total obligations	92,000		83,614
Less amount included in accrued expenses	10,371		11,666
Noncurrent obligations	$	81,629	$	71,948

As of December 31, 2012, the Company had $61.1 million in surety bonds and letters of credit outstanding to secure workers' compensation obligations.

Employee Benefit Plans

12 Months Ended

Dec. 31, 2012

Pension and Other Postretirement Benefit Expense [Abstract]

Employee Benefit Plans

Defined Benefit Pension and Other Postretirement Benefit Plans

The Company provides funded and unfunded non-contributory defined benefit pension plans covering certain of its salaried and hourly employees. Benefits are generally based on the employee's age and compensation. The Company funds the plans in an amount not less than the minimum statutory funding requirements or more than the maximum amount that can be deducted for U.S. federal income tax purposes.

The Company also currently provides certain postretirement medical and life insurance coverage for eligible employees. Generally, covered employees who terminate employment after meeting eligibility requirements are eligible for postretirement coverage for themselves and their dependents. The salaried employee postretirement benefit plans are contributory, with retiree contributions adjusted annually, and contain other cost-sharing features such as deductibles and coinsurance. The Company's current funding policy is to fund the cost of all postretirement benefits as they are paid.

Employees acquired with the ICG acquisition were brought over in their existing plan. Subsequently, the terms of the plan were amended to change vesting periods, coverage caps, and eligible ages, resulting in a reduction of the benefit obligation of $55.5 million.

Obligations and Funded Status.

Summaries of the changes in the benefit obligations, plan assets and funded status of the plans are as follows:



							Other Postretirement
	Pension Benefits						Benefits
	2012			2011			2012			2011
	(In thousands)
CHANGE IN BENEFIT OBLIGATIONS
Benefit obligations at January 1	$	333,951		$	297,707		$	45,129		$	39,633
Service cost	27,466			16,490			2,142			3,917
Interest cost	15,668			16,253			2,020			3,279
Plan amendments	—			(3,235		)	2,183			(55,542		)
Benefits paid	(23,624		)	(18,848		)	(4,244		)	(1,669		)
Curtailments	(687		)	—			(708		)	—
Acquisition of ICG	—			—			—			48,441
Other-primarily actuarial loss (gain)	38,120			25,584			2,804			7,070
Benefit obligations at December 31	$	390,894		$	333,951		$	49,326		$	45,129
CHANGE IN PLAN ASSETS
Value of plan assets at January 1	$	285,074		$	247,713		$	—		$	—
Actual return on plan assets	42,396			9,443			—			—
Employer contributions	19,028			46,766			4,244			1,669
Benefits paid	(23,624		)	(18,848		)	(4,244		)	(1,669		)
Value of plan assets at December 31	$	322,874		$	285,074		$	—		$	—
Accrued benefit cost	(68,020		)	(48,877		)	(49,326		)	(45,129		)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit (cost)	$	1,890		$	1,736		$	45,938		$	62,920
Accumulated gain (loss)	(68,915		)	(68,302		)	(1,531		)	1,795
	$	(67,025	)	$	(66,566	)	$	44,407		$	64,715
BALANCE SHEET AMOUNTS
Current liability	$	(390	)	$	(633	)	$	(4,240	)	$	(2,820	)
Noncurrent liability	$	(67,630	)	$	(48,244	)	$	(45,086	)	$	(42,309	)
	$	(68,020	)	$	(48,877	)	$	(49,326	)	$	(45,129	)

Pension Benefits

The accumulated benefit obligation for all pension plans was $366.1 million and $314.7 million at December 31, 2012 and 2011, respectively. The accumulated benefit obligation differs from the benefit obligation in that it includes no assumption about future compensation levels.

The benefit obligation and the accumulated benefit obligation for the Company's unfunded pension plan were $10.6 million and $9.4 million, respectively, at December 31, 2012.

The prior service credit and net loss that will be amortized from accumulated other comprehensive income into net periodic benefit cost in 2013 are $0.2 million and $16.2 million, respectively.

Other Postretirement Benefits

The prior service credit and net gain that will be amortized from accumulated other comprehensive income into net periodic benefit cost in 2013 is $11.0 million and $0.3 million, respectively.

Components of Net Periodic Benefit Cost. The following table details the components of pension benefit costs:



	Pension Benefits									Other Postretirement Benefits
Year Ended December 31,	2012			2011			2010			2012			2011			2010
	(In thousands)
Service cost	$	27,466		$	16,490		$	15,870		$	2,142		$	3,917		$	1,509
Interest cost	15,668			16,253			15,822			2,020			3,279			2,083
Curtailments	324			—			—			(4,049		)	—			—
Expected return on plan assets*	(22,030		)	(21,812		)	(19,392		)	—			—			—
Amortization of prior service cost (credit)	259			(189		)	173			(11,458		)	(2,364		)	(2,364		)
Amortization of other actuarial losses (gains)	14,666			8,748			7,130			(522		)	(3,100		)	(2,918		)
Net benefit cost	$	36,353		$	19,490		$	19,603		$	(11,867	)	$	1,732		$	(1,690	)

*The Company does not fund its other postretirement benefit obligations.

The differences generated from changes in assumed discount rates and returns on plan assets are amortized into earnings over a five-year period.

Assumptions. The following table provides the assumptions used to determine the actuarial present value of projected benefit obligations at December 31.



			Other
	Pension		Postretirement
	Benefits		Benefits
	2012	2011	2012	2011
Weighted average assumptions:
Discount rate	4.13%	4.91%	3.64%	4.52%
Rate of compensation increase	3.39%	3.39%	N/A	N/A

The following table provides the assumptions used to determine net periodic benefit cost for years ended December 31.



	Pension Benefits			Other Postretirement Benefits
	2012	2011	2010	2012	2011	2010
Weighted average assumptions:
Discount rate	4.91%	5.71%	5.97%	4.52%	5.23%	5.67%
Rate of compensation increase	3.39%	3.39%	3.39%	N/A	N/A	N/A
Expected return on plan assets	7.75%	8.50%	8.50%	N/A	N/A	N/A

The Company establishes the expected long-term rate of return at the beginning of each fiscal year based upon historical returns and projected returns on the underlying mix of invested assets. The Company utilizes modern portfolio theory modeling techniques in the development of its return assumptions. This technique projects rates of return that can be generated through various asset allocations that lie within the risk tolerance set forth by members of the Company's pension committee (the "Pension Committee"). The risk assessment provides a link between a pension's risk capacity, management's willingness to accept investment risk and the asset allocation process, which ultimately leads to the return generated by the invested assets.

The health care cost trend rate assumed for 2013 is 7.5% and is expected to reach an ultimate trend rate of 4.5% by 2028. A one-percentage-point increase in the health care cost trend rate would have increased the postretirement benefit obligation at December 31, 2012 by $1.0 million. A one-percentage-point decrease in the health care cost trend rate would have decreased the postretirement benefit obligation at December 31, 2012 by $0.8 million. The effect of these changes would have had an insignificant impact on the net periodic postretirement benefit costs.

Plan Assets

The Pension Committee is responsible for overseeing the investment of pension plan assets. The Pension Committee is responsible for determining and monitoring appropriate asset allocations and for selecting or replacing investment managers, trustees and custodians. The pension plan's current investment targets are 65% equity, 30% fixed income securities and 5% cash. The Pension Committee reviews the actual asset allocation in light of these targets on a periodic basis and rebalances among investments as necessary. The Pension Committee evaluates the performance of investment managers as compared to the performance of specified benchmarks and peers and monitors the investment managers to ensure adherence to their stated investment style and to the plan's investment guidelines.

The Company's pension plan assets at December 31, 2012 and 2011, respectively, are categorized below according to the fair value hierarchy as defined in Note 11, "Fair Value Measurements":



	Total				Level 1				Level 2				Level 3
	2012		2011		2012		2011		2012		2011		2012		2011
	(In thousands)
Equity Securities:^(A)
U.S. small-cap	$	13,099	$	11,178	$	13,099	$	11,178	$	—	$	—	$	—	$	—
U.S. mid-cap	43,946		50,264		12,717		23,474		31,229		26,790		—		—
U.S. large-cap	102,922		91,561		48,536		44,820		54,386		46,741		—		—
Non-U.S.	27,251		22,509		—		—		27,251		22,509		—		—
Fixed income securities:
U.S. government securities^(B)	24,202		13,454		23,483		12,738		719		716		—		—
Non-U.S. government securities^(C)	3,681		2,968		—		—		3,681		2,968		—		—
U.S. government asset and mortgage backed securities^(D)	781		800		—		—		781		800		—		—
Corporate fixed income^(E)	14,016		14,004		—		—		14,016		14,004		—		—
State and local government securities^(F)	9,903		18,416		—		—		9,903		18,416		—		—
Other fixed income^(G)	61,765		51,470		—		—		61,765		51,470		—		—
Short-term investments^(H)	20,894		8,029		—		—		20,894		8,029		—		—
Other investments^(I)	414		421		—		—		414		421		—		—
Total	$	322,874	$	285,074	$	97,835	$	92,210	$	225,039	$	192,864	$	—	$	—

(A) Equity securities includes investments in 1) common stock, 2) preferred stock and 3) mutual funds. Investments in common and preferred stocks are valued using quoted market prices multiplied by the number of shares owned. Investments in mutual funds are valued at the net asset value per share multiplied by the number of shares held as of the measurement date and are traded on listed exchanges.

(B) U.S. government securities includes agency and treasury debt. These investments are valued using dealer quotes in an active market.

(C) Non-U.S. government securities includes debt securities issued by foreign governments and are valued utilizing a price spread basis valuation technique with observable sources from investment dealers and research vendors.

(D) U.S. government asset and mortgage backed securities includes government-backed mortgage funds which are valued utilizing an income approach that includes various valuation techniques and sources such as discounted cash flows models, benchmark yields and securities, reported trades, issuer trades and/or other applicable data.

(E) Corporate fixed income is primarily comprised of corporate bonds and certain corporate asset-backed securities that are denominated in the U.S. dollar and are investment-grade securities. These investments are valued using dealer quotes.

(F) State and local government securities include different U.S. state and local municipal bonds and asset backed securities, these investments are valued utilizing a market approach that includes various valuation techniques and sources such as value generation models, broker quotes, benchmark yields and securities, reported trades, issuer trades and/or other applicable data.

(G) Other fixed income investments are actively managed fixed income vehicles that are valued at the net asset value per share multiplied by the number of shares held as of the measurement date.

(H) Short-term investments include governmental agency funds, government repurchase agreements, commingled funds, and pooled funds and mutual funds. Governmental agency funds are valued utilizing an option adjusted spread valuation technique and sources such as interest rate generation processes, benchmark yields and broker quotes. Investments in governmental repurchase agreements, commingled funds and pooled funds and mutual funds are valued at the net asset value per share multiplied by the number of shares held as of the measurement date.

(I) Other investments includes cash, forward contracts, derivative instruments, credit default swaps, interest rate swaps and mutual funds. Investments in interest rate swaps are valued utilizing a market approach that includes various valuation techniques and sources such as value generation models, broker quotes in active and non-active markets, benchmark yields and securities, reported trades, issuer trades and/or other applicable data. Forward contracts and derivative instruments are valued at their exchange listed price or broker quote in an active market. The mutual funds are valued at the net asset value per share multiplied by the number of shares held as of the measurement date and are traded on listed exchanges.

Cash Flows. The Company expects to make contributions of $0.9 million to the pension plans in 2013, which is impacted by the Moving Ahead for Progress in the 21st Century Act (MAP-21) enacted July 6, 2012. MAP-21 does not reduce the Company's obligations under the plan, but redistributes the timing of required payments by providing near term funding relief for sponsors under the Pension Protection Act.

The following represents expected future benefit payments from the plan, which reflect expected future service, as appropriate:



			Other
	Pension		Postretirement
	Benefits		Benefits
	(In thousands)
2013	$	21,275	$	3,987
2014	23,674		4,204
2015	24,210		4,430
2016	28,464		4,720
2017	32,124		4,893
Years 2018-2022	190,016		24,895
	$	319,763	$	47,129

Other Plans

The Company sponsors savings plans which were established to assist eligible employees provide for their future retirement needs. The Company's expense, representing its contributions to the plans, was $27.2 million, $25.9 million and $18.1 million for the years ended December 31, 2012, 2011 and 2010, respectively.

- Definition

The entire disclosure for pension and other postretirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-URI http://asc.fasb.org/topic&trid=2235017

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Implementation Guide (Q and A)
-Number FAS88
-Paragraph 63
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 106
-Paragraph 518
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Emerging Issues Task Force (EITF)
-Number 03-2
-Paragraph 8
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 87
-Paragraph 264
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph q
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph h
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 8
-Subparagraph m
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5, 6, 7, 8
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 158
-Paragraph 7, 21, 22
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS106-2
-Paragraph 20, 21, 22
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 30
-Paragraph 26
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+ Details

Risk Concentrations

12 Months Ended

Dec. 31, 2012

Risks Concentrations [Abstract]

Concentration Risk Disclosure [Text Block]

Risk Concentrations

Credit Risk and Major Customers

The Company has a formal written credit policy that establishes procedures to determine creditworthiness and credit limits for trade customers and counterparties in the over-the-counter coal market. Generally, credit is extended based on an evaluation of the customer's financial condition. Collateral is not generally required, unless credit cannot be established. Credit losses are provided for in the financial statements and historically have been minimal.

The Company markets its steam coal principally to domestic and foreign electric utilities and its metallurgical coal to domestic and foreign steel producers. Revenues from export sales were $1.2 billion, $920.0 million and $471.5 million for the years ended December 31, 2012, 2011 and 2010, respectively. As of December 31, 2012 and 2011, accounts receivable from electric utilities totaled $159.5 million and $261.2 million, respectively, or 65% and 69% of total trade receivables, respectively. As of December 31, 2012 and 2011, accounts receivable from sales of metallurgical-quality coal totaled $86.6 million and $117.4 million, respectively, or 35% and 31%, of total trade receivables, respectively.

The Company uses shipping destination as the basis for attributing revenue to individual countries. The Company's foreign revenues by geographical location for the year ended December 31, 2012, follows:



	December 31, 2012
	(In thousands)
Europe (including Morocco and Turkey)	$	674,754
Asia	203,193
North America	72,542
South America	57,184
Brokered sales	145,438
Total	$	1,153,111

The Company is committed under long-term contracts to supply steam coal that meets certain quality requirements at specified prices. These prices are generally adjusted based on indices. Quantities sold under some of these contracts may vary from year to year within certain limits at the option of the customer. The Company sold approximately 140.8 million tons of coal in 2012. Approximately 70% of this tonnage (representing approximately 50% of the Company's revenue) was sold under long-term contracts (contracts having a term of greater than one year). Long-term contracts range in remaining life from one to eight years.

Third-party sources of coal

The Company uses independent contractors to mine coal at certain mining complexes. The Company also purchases coal from third parties that it sells to customers. Factors beyond the Company's control could affect the availability of coal produced for or purchased by the Company. Disruptions in the quantities of coal produced for or purchased by the Company could impair its ability to fill customer orders or require it to purchase coal from other sources at prevailing market prices in order to satisfy those orders.

Transportation

The Company depends upon barge, rail, truck and belt transportation systems to deliver coal to its customers. Disruption of these transportation services due to weather-related problems, mechanical difficulties, strikes, lockouts, bottlenecks, and other events could temporarily impair the Company's ability to supply coal to its customers, resulting in decreased shipments. In the past, disruptions in rail service have resulted in missed shipments and production interruptions.

- Definition

The entire disclosure for any concentrations existing at the date of the financial statements that make an entity vulnerable to a reasonably possible, near-term, severe impact. This disclosure informs financial statement users about the general nature of the risk associated with the concentration, and may indicate the percentage of concentration risk as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6327-108592

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13531-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6404-108592

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6442-108592

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6351-108592

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13537-108611

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Statement of Position (SOP)
-Number 94-6
-Paragraph 21, 22, 24
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 15A
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Earnings Per Common Share

12 Months Ended

Dec. 31, 2012

Earnings Per Share [Abstract]

Earnings Per Common Share

. Earnings (Loss) per Common Share

The following table provides the basis for earnings (loss) per share calculations by reconciling basic and diluted weighted average shares outstanding:



	Year Ended December 31
	2012	2011	2010
	(In thousands)
Weighted average shares outstanding:
Basic weighted average shares outstanding	211,381	190,086	162,398
Effect of common stock equivalents under incentive plans	—	819	812
Diluted weighted average shares outstanding	211,381	190,905	163,210

The effect of options to purchase 5.2 million, 2.6 million and 2.5 million shares of common stock were excluded from the calculation of diluted weighted average shares outstanding for the years ended December 31, 2012, 2011 and 2010, respectively, because the exercise price of these options exceeded the average market price of the Company's common stock for this period. The weighted average share impact of options, restricted stock and restricted stock units that were excluded from the calculation of weighted average shares for the year ended December 31, 2012 due to the Company's net loss were not significant.

Leases

12 Months Ended

Dec. 31, 2012

Leases [Abstract]

Leases of Lessee Disclosure [Text Block]

. Leases

The Company leases equipment, land and various other properties under non-cancelable long-term leases, expiring at various dates. Certain leases contain options that would allow the Company to extend the lease or purchase the leased asset at the end of the base lease term. In addition, the Company enters into various non-cancelable royalty lease agreements under which future minimum payments are due.

Minimum payments due in future years under these agreements in effect at December 31, 2012 are as follows:



	Operating
	Leases		Royalties
	(In thousands)
2013	$	26,837	$	26,303
2014	25,109		35,954
2015	17,748		37,725
2016	9,708		33,833
2017	7,306		32,690
Thereafter	5,334		147,103
	$	92,042	$	313,608

Rental expense, including amounts related to these operating leases and other shorter-term arrangements, amounted to $41.2 million in 2012, $43.9 million in 2011 and $41.6 million in 2010.

Royalties are paid to lessors either as a fixed price per ton or as a percentage of the gross selling price of the mined coal. Royalties under the majority of the Company's significant leases are paid on the percentage of gross selling price basis. Royalty expense, including production royalties, was $302.0 million in 2012, $349.0 million in 2011 and $286.8 million in 2010.

As of December 31, 2012, certain of the Company's lease obligations were secured by outstanding surety bonds totaling $60.7 million.

- Definition

The entire disclosure for lessee entity's leasing arrangements including, but not limited to, all of the following: (a.) The basis on which contingent rental payments are determined, (b.) The existence and terms of renewal or purchase options and escalation clauses, (c.) Restrictions imposed by lease agreements, such as those concerning dividends, additional debt, and further leasing.

+ References + Details

Transactions with Patriot Coal Corporation	12 Months Ended
Transactions with Patriot Coal Corporation	Dec. 31, 2012
Guarantees [Abstract]
Guarantees	Transactions with Patriot Coal Corporation On December 31, 2005, Arch entered into a purchase and sale agreement to sell mining complexes to Magnum Coal Company (“Magnum”). On July 23, 2008, Patriot Coal Corporation acquired Magnum from Arc Light Capital Partners. On July 9, 2012, Patriot Coal Corporation and certain of its wholly owned subsidiaries, including Magnum, (collectively, “Patriot”) filed voluntary petitions for reorganization under Chapter 11 of the U.S. Code in the U.S. Bankruptcy Court for the Southern District of New York ("Bankruptcy Court"). The Company has agreed to continue to provide surety bonds and letters of credit for certain Magnum obligations, primarily reclamation. The surety bonding amounts are mandated by the state and are not directly related to the estimated cost to reclaim the properties. At December 31, 2012, the Company had $34.4 million of surety bonds remaining related to Magnum properties, however Patriot Coal has posted letters of credit of $16.7 million in the Company’s favor. On September 20, 2012, Patriot filed a motion with the Bankruptcy Court to reject a master coal sales agreement entered into on December 31, 2005 between the Company and Magnum, which was established in order to meet obligations under a coal sales agreement with a customer who did not consent to the assignment of their contract to Magnum. On December 18, 2012, the court accepted Patriot's motion to reject the master coal sales agreement. As a result of the court's decision, the Company accrued $58.3 million, which represents the discounted cash flows of the remaining monthly buyout amounts under the underlying coal sales agreement. The current liability for this obligation was $7.6 million at December 31, 2012.

Contingencies	12 Months Ended
Contingencies	Dec. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Commitments and Contingencies Allegheny Energy Supply (“Allegheny”), the sole customer of coal produced at the Company’s subsidiary Wolf Run Mining Company’s (“Wolf Run”) Sycamore No. 2 mine, filed a lawsuit against Wolf Run, Hunter Ridge Holdings, Inc. (“Hunter Ridge”), and ICG in state court in Allegheny County, Pennsylvania on December 28, 2006, and amended its complaint on April 23, 2007. Allegheny claimed that Wolf Run breached a coal supply contract when it declared force majeure under the contract upon idling the Sycamore No. 2 mine in the third quarter of 2006, and that Wolf Run continued to breach the contract by failing to ship in volumes referenced in the contract. The Sycamore No. 2 mine was idled after encountering adverse geologic conditions and abandoned gas wells that were previously unidentified and unmapped. After extensive searching for gas wells and rehabilitation of the mine, it was re-opened in 2007, but with notice to Allegheny that it would necessarily operate at reduced volumes in order to safely and effectively avoid the many gas wells within the reserve. The amended complaint also alleged that the production stoppages constitute a breach of the guarantee agreement by Hunter Ridge and breach of certain representations made upon entering into the contract in early 2005. Allegheny voluntarily dropped the breach of representation claims later. Allegheny claimed that it would incur costs in excess of $100 million to purchase replacement coal over the life of the contract. ICG, Wolf Run and Hunter Ridge answered the amended complaint on August 13, 2007, disputing all of the remaining claims. On November 3, 2008, ICG, Wolf Run and Hunter Ridge filed an amended answer and counterclaim against the plaintiffs seeking to void the coal supply agreement due to, among other things, fraudulent inducement and conspiracy. On September 23, 2009, Allegheny filed a second amended complaint alleging several alternative theories of liability in its effort to extend contractual liability to ICG, which was not a party to the original contract and did not exist at the time Wolf Run and Allegheny entered into the contract. No new substantive claims were asserted. ICG answered the second amended complaint on October 13, 2009, denying all of the new claims. ICG’s counterclaim was dismissed on motion for summary judgment entered on May 11, 2010. Allegheny’s claims against ICG were also dismissed by summary judgment, but the claims against Wolf Run and Hunter Ridge were not. The court conducted a non-jury trial of this matter beginning on January 10, 2011 and concluding on February 1, 2011. At the trial, Allegheny presented its evidence for breach of contract and claimed that it is entitled to past and future damages in the aggregate of between $228.0 million and $377.0 million. Wolf Run and Hunter Ridge presented their defense of the claims, including evidence with respect to the existence of force majeure conditions and excuse under the contract and applicable law. Wolf Run and Hunter Ridge presented evidence that Allegheny’s damage calculations were significantly inflated because they were not determined as of the time of the breach and, in some instances, artificially assumed future non-delivery or did not take into account the apparent requirement to supply coal in the future. On May 2, 2011, the trial court entered a Memorandum and Verdict determining that Wolf Run had breached the coal supply contract and that the performance shortfall was not excused by force majeure. ICG and Allegheny filed post-verdict motions in the trial court and on August 23, 2011, the court denied the parties’ motions. The court entered a final judgment on August 25, 2011, in the amount of $104.1 million, which included pre-judgment interest. The parties appealed the lower court’s decision to the Superior Court of Pennsylvania. Wolf Run and Hunter Ridge have filed an appeal bond in the amount of $124.9 million. On August 13, 2012, the Superior Court of Pennsylvania ruled that the lower court should have calculated damages as of the date of breach, and remanded the matter back to the lower court with instructions to recalculate the award. This ruling resulted in a reduction of the Company's best estimate of the probable loss related to this lawsuit. On November 19, 2012, Allegheny filed a Petition for Allowance of Appeal with the Supreme Court of Pennsylvania and Wolf Run and Hunter Ridge filed an Answer. This Petition is pending. In addition, the Company is a party to numerous claims and lawsuits with respect to various matters. The Company provides for costs related to contingencies when a loss is probable and the amount is reasonably determinable. As of December 31, 2012 and December 31, 2011, the Company had accrued $32.8 million and $117.2 million, respectively, for all legal matters, including $4.4 million and $6.3 million classified as current. The ultimate resolution of any such legal matter could result in outcomes which may be materially different from amounts the Company has accrued for such matters. The Company has unconditional purchase obligations relating to purchases of coal, materials and supplies and capital commitments, other than reserve acquisitions, and is also a party to transportation capacity commitments. The future commitments under these agreements total $216.2 million in 2013, $135.3 million in 2014, $135.1 million in 2015, $102.5 million in 2016, $98.6 million in 2017 and $445.6 million thereafter. During the years ended December 31, 2012, 2011 and 2010, the Company fulfilled its commitments under agreements containing unconditional obligations.

- Definition

The entire disclosure for commitments and contingencies.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 20
-Section 50
-Paragraph 1
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-Subparagraph (SX 210.5-02.25)
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Interpretation (FIN)
-Number 14
-Paragraph 3
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 5
-Paragraph 9, 10, 11, 12
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Segment Information

12 Months Ended

Dec. 31, 2012

Segment Reporting [Abstract]

Segment Reporting Disclosure [Text Block]

Segment Information

The Company has three reportable business segments, which are based on the major coal producing basins in which the Company operates. Each of these reportable business segments includes a number of mine complexes. The Company manages its coal sales by coal basin, not by individual mine complex. Geology, coal transportation routes to customers, regulatory environments and coal quality are characteristic to a basin. Accordingly, market and contract pricing have developed by coal basin. Mine operations are evaluated based on their per-ton operating costs (defined as including all mining costs but excluding pass-through transportation expenses), as well as on other non-financial measures, such as safety and environmental performance. The Company’s reportable segments are the Powder River Basin (PRB) segment, with operations in Wyoming; the Western Bituminous (WBIT) segment, with operations in Utah, Colorado and southern Wyoming; the Appalachia (APP) segment, with operations in West Virginia, Kentucky, Maryland and Virginia. The “Other” operating segment represents primarily the Company’s Illinois operations and ADDCAR subsidiary, which manufactures and sells its patented highwall mining system.

Operating segment results for the years ended December 31, 2012, 2011 and 2010 are presented below. Results for the reportable segments include all direct costs of mining, including all depreciation, depletion and amortization related to the mining operations, even if the assets are not recorded at the operating segment level. These reportable segments results do not reflect the mine closure or impairment costs, since those are not reflected in the operating income reviewed by management. Corporate, Other and Eliminations includes these charges, as well as the change in fair value of coal derivatives and coal trading activities, net; corporate overhead; land management; other support functions; and the elimination of intercompany transactions.

The asset amounts below represent an allocation of assets consistent with the basis used for the Company’s incentive compensation plans. The amounts in Corporate, Other and Eliminations represent primarily corporate assets (cash, receivables, investments, plant, property and equipment) as well as unassigned coal reserves, above-market acquired sales contracts and other unassigned assets. Goodwill is allocated to the respective reporting units, even though it may not be reflected in the subsidiaries’ financial statements.



	PRB			APP			WBIT		Other Operating Segments			Corporate, Other and Eliminations			Consolidated
	(in thousands)
December 31, 2012

Revenues	$	1,524,537		$	1,793,575		$	728,089	$	112,837		$	—		$	4,159,038
Income (loss) from operations	100,679			148,512			144,421		5,145			(1,080,345		)	(681,588		)
Depreciation, depletion and amortization	166,539			271,220			71,696		11,512			4,541			525,508
Amortization of acquired sales contracts, net	(1,987		)	(23,925		)	—		723			—			(25,189		)
Total assets	1,972,522			3,875,105			658,255		176,032			3,324,863			10,006,777
Capital expenditures	23,410			275,476			58,465		9,928			27,946			395,225

December 31, 2011
Revenues	$	1,646,947		$	1,915,090		$	672,766	$	51,092		$	—		$	4,285,895
Income (loss) from operations	180,730			283,404			119,665		(4,685		)	(165,538		)	413,576
Depreciation, depletion and amortization	171,693			203,759			81,235		7,876			2,024			466,587
Amortization of acquired sales contracts, net	19,458			(39,988		)	—		(1,539		)	—			(22,069		)
Total assets	2,307,783			4,740,723			681,393		581,040			1,903,020			10,213,959
Capital expenditures	110,999			217,435			66,356		28,243			117,903			540,936

December 31, 2010
Revenues	$	1,606,236		$	1,042,490		$	537,542	$	—		$	—		$	3,186,268
Income (loss) from operations	146,555			193,943			58,082		—			(74,596		)	323,984
Depreciation, depletion and amortization	185,218			97,764			80,497		—			1,587			365,066
Amortization of acquired sales contracts, net	35,606			—			—		—			—			35,606
Total assets	2,295,786			706,624			677,611		—			1,200,748			4,880,769
Capital expenditures	38,142			70,839			65,470		—			140,206			314,657

A reconciliation of segment income from operations to consolidated income before income taxes follows:



		December 31
		2012			2011			2010
	(In thousands)
Income (loss) from operations		$	(681,588	)	$	413,576		$	323,984
Interest expense		(317,626		)	(230,186		)	(142,549		)
Interest income		5,478			3,309			2,449
Other nonoperating expense		(23,668		)	(51,448		)	(6,776		)
Income (loss) before income taxes		$	(1,017,404	)	$	135,251		$	177,108

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8981-108599

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-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 131
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Quarterly Financial Information

12 Months Ended

Dec. 31, 2012

Quarterly Financial Information [Abstract]

Quarterly Financial Information [Text Block]

Quarterly Financial Information (Unaudited)

Quarterly financial data for the years ended December 31, 2012 and 2011 is summarized below:



	March 31		June 30			September 30			December 31
			(a)(b)			(a)			(b)
	(In thousands, except per share data)
2012:
Revenues	$	1,039,651	$	1,063,538		$	1,087,618		$	968,231
Gross profit	63,704		54,984			69,249			37,176
Mine closure and asset impairment costs	—		525,762			(2,194		)	—
Goodwill and other intangible asset impairment	—		115,791			—			230,632
Income from operations	54,081		(588,984		)	135,960			(282,645		)
Net income (loss)	1,409		(435,424		)	45,751			(295,423		)
Basic earnings (loss) per common share	$	0.01	$	(2.05	)	$	0.22		$	(1.39	)
Diluted earnings (loss) per common share	$	0.01	$	(2.05	)	$	0.22		$	(1.39	)



	March 31		June 30		September 30		December 31
			(c)		(c)		(c)
	(In thousands, except per share data)
2011:
Revenues	$	872,938	$	985,528	$	1,198,673	$	1,228,756
Gross profit	130,523		172,234		120,085		154,388
Income from operations	102,238		95,354		76,256		139,728
Net income	55,874		6,630		9,121		71,215
Basic earnings per common share	$	0.34	$	0.04	$	0.04	$	0.34
Diluted earnings per common share	$	0.34	$	0.04	$	0.04	$	0.33

(a) The Company's results in 2012 were impacted by challenging market conditions. In response to these conditions, the Company made the decision to close or idle 10 mines in Appalachia and curtailed production at other thermal mines. See Note 3, "Mine Closure and Asset Impairment Costs".

(b) Challenging markets also resulted in impairment charges to goodwill relating to the Black Thunder mining complex in the second quarter of 2012 and two mines in Appalachia in the fourth quarter of 2012. See Note 7, "Goodwill".

(c) The Company expensed costs related to the June 2011 acquisition of ICG $98.2 million, $4.7 million and $1.3 million in the second, third and fourth quarters of 2011, respectively.

- Definition

The entire disclosure for the quarterly financial data in the annual financial statements. The disclosure may include a tabular presentation of financial information for each fiscal quarter for the current and previous year, including revenues, gross profit, income or loss before extraordinary items and earnings per share data. It also includes an indication if the information in the note is unaudited, comments on the aggregate effect of year-end adjustments, and an explanation of matters or transactions that affect comparability or are pertinent to an understanding of the information furnished.

+ References + Details

Supplemental Condensed Consolidating Financial Information

12 Months Ended

Dec. 31, 2012

Supplemental Condensed Consolidating Financial Information [Abstract]

Supplemental Condensed Consolidating Financial Information Text Block

Supplemental Condensed Consolidating Financial Information

Pursuant to the indentures governing Arch Coal, Inc.’s senior notes, certain wholly-owned subsidiaries of the Company have fully and unconditionally guaranteed the senior notes on a joint and several basis. The following tables present condensed consolidating financial information for (i) the Company, (ii) the issuer of the senior notes, (iii) the guarantors under the senior notes, and (iv) the entities which are not guarantors under the senior notes (Arch Receivable Company, LLC and the Company’s subsidiaries outside the U.S.):

Condensed Consolidating Statements of Operations

Year Ended December 31, 2012



	Parent/Issuer			Guarantor Subsidiaries			Non- Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Revenues	$	—		$	4,159,038		$	—		$	—		$	4,159,038
Costs, expenses and other
Cost of sales	10,918			3,427,095			—			—			3,438,013
Depreciation, depletion and amortization	5,392			520,083			33			—			525,508
Amortization of acquired sales contracts, net	—			(25,189		)	—			—			(25,189		)
Change in fair value of coal derivatives and coal trading activities, net	—			(16,590		)	—			—			(16,590		)
Coal derivative settlements, non-hedging	—			(43,990		)	—			—			(43,990		)
Selling, general and administrative expenses	84,198			41,316			8,785			—			134,299
Contract settlement resulting from Patriot Coal bankruptcy	—			58,335			—			—			58,335
Legal contingencies	—			(79,532		)	—			—			(79,532		)
Mine closure and asset impairment costs	—			523,568			—			—			523,568
Goodwill and other intangible asset impairment	—			346,423			—			—			346,423
Other operating income, net	(13,391		)	9,559			(16,387		)	—			(20,219		)
	87,117			4,761,078			(7,569		)	—			4,840,626
Income from investment in subsidiaries	(569,795		)	—			—			569,795			—
Income (loss) from operations	(656,912		)	(602,040		)	7,569			569,795			(681,588		)
Interest expense, net:
Interest expense	(366,614		)	(35,207		)	(3,221		)	87,416			(317,626		)
Interest income	28,097			57,303			7,494			(87,416		)	5,478
	(338,517		)	22,096			4,273			—			(312,148		)
Other nonoperating expense
Net loss resulting from early retirement and refinancing of debt	(21,975		)	(1,693		)	—			—			(23,668		)
Bridge financing costs related to ICG	—			—			—			—			—
	(21,975		)	(1,693		)	—			—			(23,668		)
Income (loss) before income taxes	(1,017,404		)	(581,637		)	11,842			569,795			(1,017,404		)
Provision for (benefit from) income taxes	(333,717		)	—			—			—			(333,717		)
Net income (loss)	(683,687		)	(581,637		)	11,842			569,795			(683,687		)
Less: Net income attributable to noncontrolling interest	(268		)	—			—			—			(268		)
Net income (loss) attributable to Arch Coal, Inc.	$	(683,955	)	$	(581,637	)	$	11,842		$	569,795		$	(683,955	)
Total comprehensive income (loss)	$	(692,239	)	$	(587,616	)	$	11,842		$	575,774		$	(692,239	)

Condensed Consolidating Statements of Operations

Year Ended December 31, 2011



	Parent/Issuer			Guarantor Subsidiaries			Non- Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Revenues	$	—		$	4,285,895		$	—		$	—		$	4,285,895
Costs, expenses and other
Cost of sales	22,926			3,244,984			—			—			3,267,910
Depreciation, depletion and amortization	2,876			463,711						—			466,587
Amortization of acquired sales contracts, net	—			(22,069		)	—			—			(22,069		)
Change in fair value of coal derivatives and coal trading activities, net	—			(2,907		)	—			—			(2,907		)
Coal derivative settlements, non-hedging	—			7			—			—			7
Selling, general and administrative expenses	74,589			40,940			3,527			—			119,056
Mine closure and asset impairment costs	7,316			—			—			—			7,316
Acquisition and transition costs	47,360			—			—			—			47,360
Other operating income, net	(23,306		)	12,615			(250		)	—			(10,941		)
	131,761			3,737,281			3,277			—			3,872,319
Income from investment in subsidiaries	556,442			—			—			(556,442		)	—
Income (loss) from operations	424,681			548,614			(3,277		)	(556,442		)	413,576
Interest expense, net:
Interest expense	(256,221		)	(46,565		)	(2,224		)	74,824			(230,186		)
Interest income	16,281			55,072			6,780			(74,824		)	3,309
	(239,940		)	8,507			4,556			—			(226,877		)
Other nonoperating expense
Net loss resulting from early retirement and refinancing of debt	—			(1,958		)	—			—			(1,958		)
Bridge financing costs related to ICG	(49,490		)	—			—			—			(49,490		)
	(49,490		)	(1,958		)	—			—			(51,448		)
Income (loss) before income taxes	135,251			555,163			1,279			(556,442		)	135,251
Provision for (benefit from) income taxes	(7,589		)	—			—			—			(7,589		)
Net income (loss)	142,840			555,163			1,279			(556,442		)	142,840
Less: Net income attributable to noncontrolling interest	(1,157		)	—			—			—			(1,157		)
Net income (loss) attributable to Arch Coal, Inc.	$	141,683		$	555,163		$	1,279		$	(556,442	)	$	141,683
Total comprehensive income (loss)	$	141,240		$	552,663		$	1,279		$	(553,942	)	$	141,240

Condensed Consolidating Statements of Operations

Year Ended December 31, 2010



	Parent/Issuer			Guarantor Subsidiaries			Non- Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Revenues	$	—		$	3,186,268		$	—		$	—		$	3,186,268
Costs, expenses and other
Cost of sales	11,523			2,384,289			—			—			2,395,812
Depreciation, depletion and amortization	2,933			362,133			—			—			365,066
Amortization of acquired sales contracts, net	—			35,606			—			—			35,606
Change in fair value of coal derivatives and coal trading activities, net	—			8,924			—			—			8,924
Coal derivative settlements, non-hedging	—			(4,542		)	—			—			(4,542		)
Selling, general and administrative expenses	79,580			36,091			2,506			—			118,177
Gain on Knight Hawk transaction	—			(41,577		)	—			—			(41,577		)
Other operating income, net	(10,258		)	(4,924		)	—			—			(15,182		)
	83,778			2,776,000			2,506			—			2,862,284
Income from investment in subsidiaries	393,363			—			—			(393,363		)	—
Income (loss) from operations	309,585			410,268			(2,506		)	(393,363		)	323,984
Interest expense, net:
Interest expense	(143,606		)	(64,377		)	(2,849		)	68,283			(142,549		)
Interest income	11,129			52,899			6,704			(68,283		)	2,449
	(132,477		)	(11,478		)	3,855			—			(140,100		)
Other nonoperating expense
Net loss resulting from early retirement and refinancing of debt	—			(6,776		)	—			—			(6,776		)
Bridge financing costs related to ICG	—			—			—			—			—
	—			(6,776		)	—			—			(6,776		)
Income (loss) before income taxes	177,108			392,014			1,349			(393,363		)	177,108
Provision for (benefit from) income taxes	17,714			—			—			—			17,714
Net income (loss)	159,394			392,014			1,349			(393,363		)	159,394
Less: Net income attributable to noncontrolling interest	(537		)	—			—			—			(537		)
Net income (loss) attributable to Arch Coal, Inc.	$	158,857		$	392,014		$	1,349		$	(393,363	)	$	158,857
Total comprehensive income (loss)	$	172,885		$	400,664		$	1,349		$	(402,013	)	$	172,885

Condensed Consolidating Balance Sheets

December 31, 2012



	Parent/Issuer			Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Assets
Cash and cash equivalents	$	671,313		$	100,468	$	12,841		$	—		$	784,622
Restricted cash	3,453			—		—			—			3,453
Short term investments	234,305			—		—			—			234,305
Receivables	49,281			40,452		247,171			(4,824		)	332,080
Inventories	—			365,424		—			—			365,424
Other	106,786			86,877		557			—			194,220
Total current assets	1,065,138			593,221		260,569			(4,824		)	1,914,104

Property, plant and equipment, net	27,476			7,309,550		72			—			7,337,098

Investment in subsidiaries	8,254,508			—		—			(8,254,508		)	—
Intercompany receivables	(1,367,739		)	1,600,311		(232,572		)	—			—
Note receivable from Arch Western	675,000			—		—			(675,000		)	—
Other	187,171			568,314		90			—			755,575
Total other assets	7,748,940			2,168,625		(232,482		)	(8,929,508		)	755,575
Total assets	$	8,841,554		$	10,071,396	$	28,159		$	(8,934,332	)	$	10,006,777

Liabilities and Stockholders’ Equity
Accounts payable	$	19,859		$	204,370	$	189		$	—		$	224,418
Accrued expenses and other current liabilities	65,293			259,162		124			(4,824		)	319,755
Current maturities of debt and short-term borrowings	32,054			842		—			—			32,896
Total current liabilities	117,206			464,374		313			(4,824		)	577,069
Long-term debt	5,061,925			23,954		—			—			5,085,879
Note payable to Arch Coal	—			675,000		—			(675,000		)	—
Asset retirement obligations	1,646			408,059		—			—			409,705
Accrued pension benefits	33,456			34,174		—			—			67,630
Accrued postretirement benefits other than pension	13,953			31,133		—			—			45,086
Accrued workers’ compensation	25,323			56,306		—			—			81,629
Deferred income taxes	664,182			—		—			—			664,182
Other noncurrent liabilities	69,296			151,360		374			—			221,030
Total liabilities	5,986,987			1,844,360		687			(679,824		)	7,152,210
Stockholders’ equity	2,854,567			8,227,036		27,472			(8,254,508		)	2,854,567
Total liabilities and stockholders’ equity	$	8,841,554		$	10,071,396	$	28,159		$	(8,934,332	)	$	10,006,777

Condensed Consolidating Balance Sheets

December 31, 2011



	Parent/Issuer			Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Assets
Cash and cash equivalents	$	61,375		$	75,425	$	1,349		$	—		$	138,149
Restricted cash	10,322			—		—			—			10,322
Short term investments	—			—		—			—			—
Receivables	65,187			27,001		378,608			(1,617		)	469,179
Inventories	—			377,490		—			—			377,490
Other	81,732			105,282		620			—			187,634
Total current assets	218,616			585,198		380,577			(1,617		)	1,182,774

Property, plant and equipment, net	21,241			7,918,816		9,093			—			7,949,150

Investment in subsidiaries	8,813,080			—		—			(8,813,080		)	—
Intercompany receivables	(1,190,342		)	1,448,902		(258,560		)	—			—
Note receivable from Arch Western	225,000			—		—			(225,000		)	—
Other	(85,668		)	1,167,501		202			—			1,082,035
Total other assets	7,762,070			2,616,403		(258,358		)	(9,038,080		)	1,082,035
Total assets	$	8,001,927		$	11,120,417	$	131,312		$	(9,039,697	)	$	10,213,959

Liabilities and Stockholders’ Equity
Accounts payable	$	30,576		$	353,180	$	26		$	—		$	383,782
Accrued expenses and other current liabilities	75,121			282,446		85			(1,617		)	356,035
Current maturities of debt and short-term borrowings	172,564			1,987		106,300			—			280,851
Total current liabilities	278,261			637,613		106,411			(1,617		)	1,020,668
Long-term debt	3,308,674			453,623		—			—			3,762,297
Note payable to Arch Coal	—			225,000		—			(225,000		)	—
Asset retirement obligations	877			445,907		—			—			446,784
Accrued pension benefits	19,198			29,046		—			—			48,244
Accrued postretirement benefits other than pension	13,843			28,466		—			—			42,309
Accrued workers’ compensation	17,272			54,676		—			—			71,948
Deferred income taxes	621,483			355,270		—			—			976,753
Other noncurrent liabilities	152,745			102,553		84			—			255,382
Total liabilities	4,412,353			2,332,154		106,495			(226,617		)	6,624,385
Redeemable noncontrolling interest	11,534			—		—			—			11,534
Stockholders’ equity	3,578,040			8,788,263		24,817			(8,813,080		)	3,578,040
Total liabilities and stockholders’ equity	$	8,001,927		$	11,120,417	$	131,312		$	(9,039,697	)	$	10,213,959

Condensed Consolidating Statements of Cash Flows

Year Ended December 31, 2012



	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$	(571,576	)	$	781,551		$	122,829		$	—		$	332,804
Investing Activities
Change in restricted cash	6,869			—			—			—			6,869
Capital expenditures	(4,424		)	(390,801		)	—			—			(395,225		)
Proceeds from dispositions of property, plant and equipment	—			1,328			21,497			—			22,825
Investments in and advances to affiliates	(6,287		)	(13,134		)	—			1,663			(17,758		)
Purchases of short term investments	(236,862		)	—			—			—			(236,862		)
Proceeds from sales of short term investments	1,754			—			—			—			1,754
Purchase of noncontrolling interest	(17,500		)	—			—			—			(17,500		)
Additions to prepaid royalties	—			(13,269		)	—			—			(13,269		)
Cash provided by (used in) investing activities	(256,450		)	(415,876		)	21,497			1,663			(649,166		)
Financing Activities
Contributions from parent	—			1,663			—			(1,663		)	—
Proceeds from the issuance of senior notes	359,753			—			—			—			359,753
Proceeds from term note issuance	1,633,500			—			—			—			1,633,500
Payments to retire debt	—			(452,934		)	—			—			(452,934		)
Net decrease in borrowings under lines of credit and commercial paper program	(375,000		)	—			(106,300		)	—			(481,300		)
Payments on term note	(7,625		)	—			—			—			(7,625		)
Net payments on other debt	(682		)	—			—			—			(682		)
Debt financing costs	(50,022		)	—			(546		)	—			(50,568		)
Dividends paid	(42,440		)	—			—			—			(42,440		)
Issuance of common stock under incentive plans	5,131			—			—			—			5,131
Transactions with affiliates, net	(84,651		)	110,639			(25,988		)	—			—
Cash provided by (used in) financing activities	1,437,964			(340,632		)	(132,834		)	(1,663		)	962,835
Increase in cash and cash equivalents	609,938			25,043			11,492			—			646,473
Cash and cash equivalents, beginning of period	61,375			75,425			1,349			—			138,149
Cash and cash equivalents, end of period	$	671,313		$	100,468		$	12,841		$	—		$	784,622

Condensed Consolidating Statements of Cash Flows

Year Ended December 31, 2011



	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$	(187,039	)	$	998,082		$	(168,801	)	$	—		$	642,242
Investing Activities
Acquisition of ICG, net of cash acquired	(2,894,339		)	—			—			—			(2,894,339		)
Change in restricted cash	5,167			—			—			—			5,167
Capital expenditures	(12,809		)	(528,021		)	(106		)	—			(540,936		)
Proceeds from dispositions of property, plant and equipment	—			25,887			—			—			25,887
Investments in and advances to affiliates	(633,534		)	(33,553		)	—			605,178			(61,909		)
Additions to prepaid royalties	—			(29,957		)	—			—			(29,957		)
Consideration paid related to prior business acquisition	(829		)	—			—			—			(829		)
Cash provided by (used in) investing activities	(3,536,344		)	(565,644		)	(106		)	605,178			(3,496,916		)
Financing Activities
Contributions from parent	—			605,178			—			(605,178		)	—
Proceeds from the issuance of senior notes	2,000,000			—			—			—			2,000,000
Proceeds from the issuance of common stock, net	1,267,933			—			—			—			1,267,933
Payments to retire debt	—			(605,178		)	—			—			(605,178		)
Net decrease in borrowings under lines of credit and commercial paper program	375,000			(56,904		)	106,300			—			424,396
Net proceeds from other debt	5,334			—			—			—			5,334
Debt financing costs	(114,799		)	(16		)	(8		)	—			(114,823		)
Dividends paid	(80,748		)	—			—			—			(80,748		)
Issuance of common stock under incentive plans	2,316			—			—			—			2,316
Transactions with affiliates, net	316,009			(379,973		)	63,964			—			—
Cash provided by (used in) financing activities	3,771,045			(436,893		)	170,256			(605,178		)	2,899,230
Increase (decrease) in cash and cash equivalents	47,662			(4,455		)	1,349			—			44,556
Cash and cash equivalents, beginning of period	13,713			79,880			—			—			93,593
Cash and cash equivalents, end of period	$	61,375		$	75,425		$	1,349		$	—		$	138,149

Condensed Consolidating Statements of Cash Flows

Year Ended December 31, 2010



	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations		Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$	(230,966	)	$	943,361		$	(15,248	)	$	—	$	697,147
Investing Activities
Capital expenditures	(4,814		)	(309,843		)	—			—		(314,657		)
Proceeds from dispositions of property, plant and equipment	—			330			—			—		330
Investments in and advances to affiliates	(13,821		)	(32,364		)	—			—		(46,185		)
Additions to prepaid royalties	—			(27,355		)	—			—		(27,355		)
Consideration paid related to prior business acquisition	(1,262		)	—			—			—		(1,262		)
Cash used in investing activities	(19,897		)	(369,232		)	—			—		(389,129		)
Financing Activities
Proceeds from the issuance of senior notes	500,000			—			—			—		500,000
Payments to retire debt	—			(505,627		)	—			—		(505,627		)
Net decrease in borrowings under lines of credit and commercial paper program	(120,000		)	7,451			(84,000		)	—		(196,549		)
Net proceeds from other debt	82			—			—			—		82
Debt financing costs	(12,022		)	(390		)	(339		)	—		(12,751		)
Dividends paid	(63,373		)	—			—			—		(63,373		)
Issuance of common stock under incentive plans	1,764			—			—			—		1,764
Contribution from non-controlling interest	891			—			—			—		891
Transactions with affiliates, net	(97,021		)	(2,566		)	99,587			—		—
Cash provided by (used in) financing activities	210,321			(501,132		)	15,248			—		(275,563		)
Increase (decrease) in cash and cash equivalents	(40,542		)	72,997			—			—		32,455
Cash and cash equivalents, beginning of period	54,255			6,883			—			—		61,138
Cash and cash equivalents, end of period	$	13,713		$	79,880		$	—		$	—	$	93,593

Accounting Policies (Policy)	12 Months Ended
Accounting Policies (Policy)	Dec. 31, 2012
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements include the accounts of Arch Coal, Inc. and its subsidiaries and controlled entities (the “Company”). The Company’s primary business is the production of thermal and metallurgical coal from surface and underground mines located throughout the United States, for sale to utility, industrial and export markets. On June 15, 2011, the Company acquired International Coal Group, Inc. (“ICG”). The Company currently operates 15 mining complexes in West Virginia, Kentucky, Maryland, Virginia, Illinois, Wyoming, Colorado and Utah. In addition, the Company has a metallurgical coal mine in development in West Virginia. All subsidiaries are wholly-owned. Intercompany transactions and accounts have been eliminated in consolidation. The Company's subsidiary Arch Western Resources, LLC (“Arch Western”) operates coal mines in Wyoming, Colorado and Utah. On April 9, 2012, Delta Housing, Inc., a subsidiary of BP p.l.c. and a joint venture partner in Arch Western, exercised their contractual right to require the Company to purchase their 0.5% common and their preferred membership interests in Arch Western. With the payment of the negotiated purchase amount of $17.5 million on July 2, 2012, Arch Western became a wholly-owned subsidiary. Accounting
Accounting Pronouncements Adopted And New Pronoucements Not Yet Implemented	Accounting Pronouncements There are no accounting pronouncements whose adoption had, or is expected to have, a material impact on the Company's consolidated financial statements.
Accounting Estimates	Accounting Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and revenues and expenses in the accompanying consolidated financial statements and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents are stated at cost. Cash equivalents consist of highly-liquid investments with an original maturity of three months or less when purchased. At December 31, 2012 and 2011, the carrying amounts of cash and cash equivalents approximate their fair value.
Allowance for Uncollectible Receivables	Allowance for Uncollectible Receivables The Company establishes an allowance for uncollectible receivables for the amounts of trade accounts receivable and other receivables that are not expected to be collected, based on past collection history, the economic environment and specified risks identified in the receivables portfolio. Receivables are considered past due if the full payment is not received by the contractual due date. At December 31, 2012 and 2011, there was either no allowance or an insignificant allowance for uncollectible receivables.
Inventories	Inventories Coal and supplies inventories are valued at the lower of average cost or market. Coal inventory costs include labor, supplies, equipment costs, transportation costs incurred prior to the transfer of title to customers and operating overhead. The costs of removing overburden, called stripping costs, incurred during the production phase of the mine are considered variable production costs and are included in the cost of the coal extracted during the period the stripping costs are incurred.
Investments and Membership Interests in Joint Ventures	Investments and Membership Interests in Joint Ventures Investments and membership interests in joint ventures are accounted for under the equity method of accounting if the Company has the ability to exercise significant influence, but not control, over the entity. The Company's share of the entity's income or loss is reflected in other operating income, net in the consolidated statements of operations. Information about investment activity is provided in Note 8, "Equity Investments and Membership Interests in Joint Ventures." Marketable equity and debt securities held by the Company that do not qualify for equity method accounting are classified as available-for-sale and are recorded at their fair value on the balance sheet. Unrealized gains and losses on these investments are recorded in other comprehensive income or loss. A decline in the value of an investment that is considered other-than-temporary would be recognized in operating expenses. Prepaid Royal
Prepaid Royalties	Prepaid Royalties Leased mineral rights are often acquired through royalty payments. When royalty payments represent prepayments recoupable against future production, they are recorded as a prepaid asset, with amounts expected to be recouped within one year classified as current. When the coal is mined under these leases the royalties are recouped and the prepayment is charged to cost of sales.
Acquired Sales Contracts	Acquired Sales Contracts Coal supply agreements (sales contracts) acquired in a business combination are capitalized at their fair value and amortized over the tons of coal shipped during the term of the contract. The fair value of a sales contract is determined by discounting the cash flows attributable to the difference between the contract price and the prevailing forward prices for the tons under contract at the date of acquisition. See Note 4, "Acquired Sales Contracts" for further information related to the Company's acquired sales contracts.
Exploration Costs	Exploration Costs Costs to acquire permits for exploration activities are capitalized. Drilling and other costs related to locating coal deposits and evaluating the economic viability of such deposits are expensed as incurred.
Property, Plant and Equipment	Plant and Equipment Plant and equipment are recorded at cost. Interest costs incurred during the construction period for major asset additions are capitalized. We capitalized $15.6 million of interests costs during the year ended December 31, 2012, while the amounts capitalized in the years ended December 31, 2011 and 2010 were insignificant. Expenditures that extend the useful lives of existing plant and equipment or increase the productivity of the asset are capitalized. The cost of maintenance and repairs that do not extend the useful life or increase the productivity of the asset are expensed as incurred. Preparation plants and loadouts are depreciated using the units-of-production method over the estimated recoverable reserves, subject to a minimum level of depreciation. Other plant and equipment are depreciated principally using the straight-line method over the estimated useful lives of the assets, limited by the remaining life of the mine. The useful lives of mining equipment, including longwalls, draglines and shovels, range from 5 to 32 years. The useful lives of buildings and leasehold improvements generally range from 10 to 30 years. Deferred Mine Development Costs of developing new mines or significantly expanding the capacity of existing mines are capitalized and amortized using the units-of-production method over the estimated recoverable reserves that are associated with the property being benefited. Costs may include construction permits and licenses; mine design; construction of access roads, shafts, slopes and main entries; and removing overburden to access reserves in a new pit. Additionally, deferred mine development includes the asset cost associated with asset retirement obligations. Coal Lands and Mineral Rights Rights to coal reserves may be acquired directly through governmental or private entities. A significant portion of the Company's coal reserves are controlled through leasing arrangements. Lease agreements are generally long-term in nature (original terms range from 10 to 50 years), and substantially all of the leases contain provisions that allow for automatic extension of the lease term providing certain requirements are met. The net book value of the Company's coal interests was $5.1 billion and $5.6 billion at December 31, 2012 and 2011. Payments to acquire royalty lease agreements and lease bonus payments are capitalized as a cost of the underlying mineral reserves and depleted over the life of proven and probable reserves. Coal lease rights are depleted using the units-of-production method, and the rights are assumed to have no residual value. Future lease bonus payments total $83.4 million in 2013, $67.3 million in 2014, $60.0 million in 2015, and $60.0 million in 2016. Depreciation, depletion and amortization. The depreciation, depletion and amortization related to long-lived assets is reflected in the statement of operations as a separate line item. No depreciation, depletion or amortization is included in any other operating cost categories. Impairment If facts and circumstances suggest that the carrying value of a long-lived asset or asset group may not be recoverable, the asset or asset group is reviewed for potential impairment. If this review indicates that the carrying amount of the asset will not be recoverable through projected undiscounted cash flows generated by the asset and its related asset group over its remaining life, then an impairment loss is recognized by reducing the carrying value of the asset to its fair value. The Company may, under certain circumstances, idle mining operations in response to market conditions or other factors. Because an idling is not a permanent closure, it is not considered an automatic indicator of impairment.
Goodwill	Goodwill In a business combination, goodwill represents the excess of the purchase price over the fair value assigned to the net tangible and identifiable intangible assets acquired. The Company tests goodwill for impairment annually as of the beginning of the fourth quarter, or when circumstances indicate a possible impairment may exist. If the results of the testing indicate that the carrying amount of a reporting unit exceeds the fair value of the reporting unit, the fair value of goodwill must be calculated. An impairment loss generally would be recognized when the carrying amount of goodwill exceeds the implied fair value of goodwill, determined by subtracting the fair value of the other assets and liabilities associated with the reporting unit from the total fair value of the reporting unit. The fair value of a reporting unit is determined using a discounted cash flow ("DCF") technique. A number of significant assumptions and estimates are involved in the application of the DCF analysis to forecast operating cash flows, including the discount rate and projections of selling prices and costs to produce.
Deferred Financing Costs	1. Accounting Policies Basis of Presentation The consolidated financial statements include the accounts of Arch Coal, Inc. and its subsidiaries and controlled entities (the “Company”). The Company’s primary business is the production of thermal and metallurgical coal from surface and underground mines located throughout the United States, for sale to utility, industrial and export markets. On June 15, 2011, the Company acquired International Coal Group, Inc. (“ICG”). The Company currently operates 15 mining complexes in West Virginia, Kentucky, Maryland, Virginia, Illinois, Wyoming, Colorado and Utah. In addition, the Company has a metallurgical coal mine in development in West Virginia. All subsidiaries are wholly-owned. Intercompany transactions and accounts have been eliminated in consolidation.
Revenue Recognition	Revenue Recognition Revenues include sales to customers of coal produced at Company operations and coal purchased from third parties. The Company recognizes revenue at the time risk of loss passes to the customer at contracted amounts. Transportation costs are included in cost of sales and amounts billed by the Company to its customers for transportation are included in revenues.
Other Operating Income, Net	Other Operating Income, Net Other operating income, net in the accompanying consolidated statements of operations reflects income and expense from sources other than physical coal sales, including: bookouts, the practice of offsetting purchase and sale contracts for shipping convenience purposes, and contract settlements; royalties earned from properties leased to third parties; income from equity investments; gains and losses from dispositions of assets; and realized gains and losses on heating oil derivatives that do not qualify for hedge accounting and are not held for trading purposes. Asset
Asset Retirement Obligations	Asset Retirement Obligations The Company's legal obligations associated with the retirement of long-lived assets are recognized at fair value at the time the obligations are incurred. Accretion expense is recognized through the expected settlement date of the obligation. Obligations are incurred at the time development of a mine commences for underground and surface mines or construction begins for support facilities, refuse areas and slurry ponds. The obligation's fair value is determined using a DCF technique and is based upon permit requirements and various estimates and assumptions that would be used by market participants, including estimates of disturbed acreage, reclamation costs and assumptions regarding equipment productivity. Upon initial recognition of a liability, a corresponding amount is capitalized as part of the carrying value of the related long-lived asset. The Company reviews its asset retirement obligation at least annually and makes necessary adjustments for permit changes as granted by state authorities and for revisions of estimates of the amount and timing of costs. For ongoing operations, adjustments to the liability result in an adjustment to the corresponding asset. For idle operations, adjustments to the liability are recognized as income or expense in the period the adjustment is recorded. Any difference between the recorded obligation and the actual cost of reclamation is recorded in profit or loss in the period the obligation is settled. See additional discussion in Note 14, "Asset Retirement Obligations."
Derivative Instruments	Derivative Instruments The Company generally utilizes derivative instruments to manage exposures to commodity prices. Additionally, the Company may hold certain coal derivative instruments for trading purposes. Derivative financial instruments are recognized in the balance sheet at fair value. Certain coal contracts may meet the definition of a derivative instrument, but because they provide for the physical purchase or sale of coal in quantities expected to be used or sold by the Company over a reasonable period in the normal course of business, they are not recognized on the balance sheet. Certain derivative instruments are designated as the hedge instrument in a hedging relationship. In a fair value hedge, the Company hedges the risk of changes in the fair value of a firm commitment, typically a fixed-price coal sales contract. Changes in both the hedged firm commitment and the fair value of a derivative used as a hedge instrument in a fair value hedge are recorded in earnings. In a cash flow hedge, the Company hedges the risk of changes in future cash flows related to a forecasted purchase or sale. Changes in the fair value of the derivative instrument used as a hedge instrument in a cash flow hedge are recorded in other comprehensive income or loss. Amounts in other comprehensive income or loss are reclassified to earnings when the hedged transaction affects earnings and are classified in a manner consistent with the transaction being hedged. The Company formally documents the relationships between hedging instruments and the respective hedged items, as well as its risk management objectives for hedge transactions. The Company evaluates the effectiveness of its hedging relationships both at the hedge's inception and on an ongoing basis. Any ineffective portion of the change in fair value of a derivative instrument used as a hedge instrument in a fair value or cash flow hedge is recognized immediately in earnings. The ineffective portion is based on the extent to which exact offset is not achieved between the change in fair value of the hedge instrument and the cumulative change in expected future cash flows on the hedged transaction from inception of the hedge in a cash flow hedge or the change in the fair value. Ineffectiveness was insignificant for the years ended December 31, 2012, 2011 and 2010. See Note 9, "Derivatives" for further disclosures related to the Company's derivative instruments.
Fair Value	Fair Value Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly hypothetical transaction between market participants at a given measurement date. Valuation techniques used must maximize the use of observable inputs and minimize the use of unobservable inputs. See Note 11, "Fair Values Measurements" for further disclosures related to the Company's recurring fair value estimates.
Income Taxes	Income Taxes Deferred income taxes are provided for temporary differences arising from differences between the financial statement amount and tax basis of assets and liabilities existing at each balance sheet date using enacted tax rates anticipated to be in effect when the related taxes are expected to be paid or recovered. A valuation allowance is established if it is more likely than not that a deferred tax asset will not be realized. In determining the need for a valuation allowance, the Company considers projected realization of tax benefits based on expected levels of future taxable income, available tax planning strategies and and the reversal of temporary differences. The benefit from tax positions that are uncertain is not recognized unless the Company concludes that it is more likely than not that the position would sustain in a dispute with taxing authorities, should the dispute be taken to the court of last resort. The Company would measure any such benefit at the largest amount of benefit that is greater than 50 percent likely of being realized upon settlement with taxing authorities. See Note 13, "Taxes" for further disclosures about income taxes.
Benefit Plans	Benefit Plans The Company has non-contributory defined benefit pension plans covering most of its salaried and hourly employees. Benefits are generally based on the employee's age and compensation. The Company also currently provides certain postretirement medical and life insurance coverage for eligible employees. The cost of providing these benefits are determined on an actuarial basis and accrued over the employee's period of active service. The Company recognizes the overfunded or underfunded status of these plans as determined on an actuarial basis on the balance sheet and the changes in the funded status are recognized in other comprehensive income. See Note 18, "Employee Benefit Plans" for additional disclosures relating to these obligations.
Stock-Based Compensation	The Company recognizes the overfunded or underfunded status of these plans as determined on an actuarial basis on the balance sheet and the changes in the funded status are recognized in other comprehensive income. See Note 18, "Employee Benefit Plans" for additional disclosures relating to these obligations. Stock-Based Compensation The compensation cost of all stock-based awards is determined based on the grant-date fair value of the award, and is recognized over the requisite service period. The grant

Debt (Tables)

12 Months Ended

Dec. 31, 2012

Debt Disclosure [Abstract]

Debt



	December 31, 2012		December 31, 2011
	(In thousands)
Indebtedness to banks under credit facilities	$	—	$	481,300
Term loan ($1.65 billion face value) due 2018	1,627,384		—
6.75% senior notes ($450.0 million face value) due 2013	—		450,971
8.75% senior notes ($600.0 million face value) due 2016	590,999		588,974
7.00% senior notes due 2019 at par	1,000,000		1,000,000
9.875% senior notes ($375.0 million face value) due 2019	360,042		—
7.25% senior notes due 2020 at par	500,000		500,000
7.25% senior notes due 2021 at par	1,000,000		1,000,000
Other	40,350		21,903
	5,118,775		4,043,148
Less current maturities of debt and short-term borrowings	32,896		280,851
Long-term debt	$	5,085,879	$	3,762,297

Mine Closure and Asset Impairment Costs (Tables)

12 Months Ended

Dec. 31, 2012

Restructuring and Related Activities [Abstract]

Schedule of Restructuring and Related Costs [Table Text Block]

The following costs are reflected in the line “Mine closure and asset impairment costs” on the consolidated statements of operations for the year ended December 31, 2012:



Parts and supplies inventory writedown	$	2,598
Impairment of property, plant and equipment	95,641
Impairment of coal properties and deferred development costs	403,279
Royalty obligations	11,546
Employee termination benefits	12,274
Pension, postretirement and occupational disease curtailment gain, net (see notes 17 and 18)	(1,770		)
	$	523,568

Acquired Sales Contracts Acquired Sales Contracts (Tables)

12 Months Ended

Dec. 31, 2012

Acquired Sales Contracts [Abstract]

Schedule Of Acquired Sales Contracts [Table Text Block]

The acquired sales contracts reflected in the consolidated balance sheets are as follows:



	December 31, 2012						December 31, 2011
	Assets			Liabilities			Assets			Liabilities
	(In thousands)						(In thousands)
Acquired fair value	$	131,819		$	166,697		$	149,457		$	166,697
Accumulated amortization	(123,776		)	(105,237		)	(115,322		)	(69,699		)
Total	$	8,043		$	61,460		$	34,135		$	96,998
Net total				$	(53,417	)				$	(62,863	)
Balance Sheet classification:
Other current	$	5,651		$	14,038		$	18,929		$	38,441
Other noncurrent	$	2,392		$	47,422		$	15,206		$	58,557

Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss) (Tables)

12 Months Ended

Dec. 31, 2012

Accumulated Other Comprehensive Income (Loss) [Abstract]

Schedule of Comprehensive Income (Loss) [Table Text Block]



				Pension,
				Postretirement
				and Other						Accumulated
				Post-						Other
	Derivative			Employment			Available-for-			Comprehensive
	Instruments			Benefits			Sale Securities			Loss
	(In thousands)
Balance at January 1, 2010	$	1,186		$	(20,539	)	$	(500	)	$	(19,853	)
2010 activity, before tax	2,711			15,406			2,877			20,994
2010 activity, tax effect	(976		)	(5,546		)	(1,036		)	(7,558		)
Balance at December 31, 2010	2,921			(10,679		)	1,341			(6,417		)
2011 activity, before tax	(11,951		)	9,345			176			(2,430		)
2011 activity, tax effect	4,301			(3,342		)	(62		)	897
Balance at December 31, 2011	(4,729		)	(4,676		)	1,455			(7,950		)
2012 activity, before tax	10,895			(21,265		)	(3,000		)	(13,370		)
2012 activity, tax effect	(3,922		)	7,655			1,080			4,813
Balance at December 31, 2012	$	2,244		$	(18,286	)	$	(465	)	$	(16,507	)

Investments in Available-for-Sale Securities (Tables)

12 Months Ended

Dec. 31, 2012

Available-for-sale Securities [Abstract]

Available-for-sale Securities [Table Text Block]

The Company's investments in available-for-sale marketable securities are as follows:



December 31, 2012										Balance Sheet
			Gross		Gross					Classification
			Unrealized		Unrealized			Fair		Short-Term		Other
	Cost Basis		Gains		Losses			Value		Investments		Assets
	(In thousands)
Available-for-sale:
U.S. government and agency securities	$	146,993	$	2	$	(412	)	$	146,583	$	146,583	$	—
Corporate notes and bonds	88,118		—		(396		)	87,722		87,722		—
Equity securities	5,271		2,704		(2,628		)	5,347		—		5,347
Total Investments	$	240,382	$	2,706	$	(3,436	)	$	239,652	$	234,305	$	5,347

The aggregate fair value of investments with unrealized losses was $223.3 million at December 31, 2012.



December 31, 2011										Balance Sheet
			Gross		Gross					Classification
			Unrealized		Unrealized			Fair		Short-Term
	Cost Basis		Gains		Losses			Value		Investments		Other Assets
	(In thousands)
Available-for-sale:
Equity securities	$	5,268	$	4,394	$	(2,122	)	$	7,540	$	—	$	7,540
Total Investments	$	5,268	$	4,394	$	(2,122	)	$	7,540	$	—	$	7,540

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 320
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27337-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27198-111563

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 320
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62586-112803

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27161-111563

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27357-111563

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27290-111563

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 19, 20, 21
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS115-1/124-1
-Paragraph 17
-Subparagraph a, b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Emerging Issues Task Force (EITF)
-Number 03-1
-Paragraph 21
-Subparagraph a, b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Goodwill Goodwill (Tables)

12 Months Ended

Dec. 31, 2012

Goodwill [Abstract]

Schedule of Goodwill [Table Text Block]

Changes in the carrying value of goodwill for the years ended December 31, 2012, 2011 and 2010 are as follows:



	(In thousands)
Balance at January 1, 2010	$	113,701
Consideration paid related to prior business acquisitions	1,262
Balance at December 31, 2010	114,963
Consideration paid related to prior business acquisitions	829
Acquisition of ICG	480,311
Balance at December 31, 2011	596,103
Impairment	(330,680		)
Balance at December 31, 2012	$	265,423

- Definition

Tabular disclosure of goodwill by reportable segment and in total which includes a rollforward schedule.

+ References + Details

Equity Investments And Membership Interests In Joint Ventures (Tables)

12 Months Ended

Dec. 31, 2012

Equity Method Investments and Joint Ventures [Abstract]

Schedule Of Summarized Financial Information Of Equity Method Investments [Table Text Block]

Summarized financial information of the Company's equity method investees follows:



	December 31
	2012		2011		2010
	(In thousands)
Condensed combined income statement information:
Revenues	$	190,661	$	184,358	$	172,933
Gross profit	15,308		19,495		25,203
Income from operations	8,898		13,180		20,243
Net income	641		6,788		16,015
Condensed combined balance sheet information:
Current assets	$	78,961	$	94,644
Noncurrent assets	387,884		331,848
Total assets	$	466,845	$	426,492
Current liabilities	$	57,403	$	51,674
Noncurrent liabilities	128,489		120,494
Equity	280,690		254,163
Noncontrolling interest	263		161
Total liabilities and equity	$	466,845	$	426,492

Schedule Of Equity Method Investments

Below are the equity method investments reflected in the consolidated balance sheets:



	Knight Hawk			DKRW			DTA			Tenaska			Millennium			Tongue River		Total
	(In thousands)
Balance at January 1, 2010	$	49,603		$	23,589		$	14,076		$	—		$	—		$	—	$	87,268
Investments in affiliates	77,637			—			—			9,768			—			—		87,405
Advances to (distributions from) affiliates, net	(12,639		)	—			4,264			—			—			—		(8,375		)
Equity in comprehensive income (loss)	16,649			(1,628		)	(3,868		)	—			—			—		11,153
Balance at December 31, 2010	$	131,250		$	21,961		$	14,472		$	9,768		$	—		$	—	$	177,451
Investments in affiliates	—			—			—			5,500			25,000			12,989		43,489
Advances to (distributions from) affiliates, net	(16,621		)	—			6,498			—			3,477			—		(6,646		)
Equity in comprehensive income (loss)	20,596			(2,246		)	(4,884		)	(2		)	(2,153		)	—		11,311
Balance at December 31, 2011	$	135,225		$	19,715		$	16,086		$	15,266		$	26,324		$	12,989	$	225,605
Investments in affiliates	—			—			—			—			—			—		—
Advances to (distributions from) affiliates, net	(7,151		)	—			4,335			—			8,798			1,708		7,690
Equity in comprehensive income (loss)	20,989			(4,200		)	(4,959		)	(2		)	(2,908		)	—		8,920
Balance at December 31, 2012	$	149,063		$	15,515		$	15,462		$	15,264		$	32,214		$	14,697	$	242,215
Notes receivable from investees:
Balance at December 31, 2011	$	—		$	30,751		$	—		$	5,059		$	—		$	—	$	35,810
Balance at December 31, 2012	$	—		$	38,680		$	—		$	5,148		$	—		$	—	$	43,828

Derivatives (Tables)

12 Months Ended

Dec. 31, 2012

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Price Risk Derivatives

At December 31, 2012, the Company held derivatives for risk management purposes that are expected to settle in the following years:



(Tons in thousands)	2013	2014	2015	Total
Coal sales	6,704	4,260	780	11,744
Coal purchases	1,410	1,260	—	2,670

Disclosure Of Fair Value Of Derivatives



	December 31, 2012								December 31, 2011
Fair Value of Derivatives	Asset			Liability					Asset			Liability
(In thousands)	Derivative			Derivative					Derivative			Derivative
Derivatives Designated as Hedging Instruments
Heating oil--diesel purchases	$	—		$	—				$	8,997		$	—
Coal	3,277			(10		)			1,109			—
Total	3,277			(10		)			10,106			—
Derivatives Not Designated as Hedging Instruments
Heating oil -- diesel purchases	7,379			—					—			—
Heating oil -- fuel surcharges	1,961			—					1,797			—
Coal -- held for trading purposes	17,403			(16,933		)			15,505			(19,927		)
Coal -- risk management	24,843			(7,342		)			14,855			(6,035		)
Total	51,586			(24,275		)			32,157			(25,962		)
Total derivatives	54,863			(24,285		)			42,263			(25,962		)
Effect of counterparty netting	(22,548		)	22,548					(18,134		)	18,134
Net derivatives as classified in the balance sheets	$	32,315		$	(1,737	)	$	30,578	$	24,129		$	(7,828	)	$	16,301



		December 31, 2012			December 31, 2011
Net derivatives as reflected on the balance sheets
Heating oil	Other current assets	$	9,340		$	10,794
Coal	Coal derivative assets	22,975			13,335
	Coal derivative liabilities	(1,737		)	(7,828		)
		$	30,578		$	16,301

Effects Of Derivatives On Measures Of Financial Performance

Derivatives used in Cash Flow Hedging Relationships (in thousands)

For the year ended December 31,



		Gain (Loss) Recognized in Other Comprehensive Income(Effective Portion)									Gains (Losses) Reclassified from Other Comprehensive Income into Income (Effective Portion)
	⁽²⁾	2012			2011			2010			2012		2011		2010
Heating oil — diesel purchases	⁽¹⁾	$	—		$	1,294		$	(149	)	$	—	$	14,866	$	437
Coal sales	⁽²⁾	7,690			4,923			(4,714		)	2,675		1,572		(1,602		)
Coal purchases		(2,440		)	(2,009		)	5,145			—		—		(1,202		)
Totals		$	5,250		$	4,208		$	282		$	2,675	$	16,438	$	(2,367	)

Derivatives Not Designated as Hedging Instruments (in thousands)

For the year ended December 31



		Gain (Loss) Recognized
		2012			2011			2010
Coal — unrealized	⁽³⁾	$	8,272		$	6,438		$	(10,991	)
Coal — realized	⁽⁴⁾	$	43,990		$	(7	)	$	4,542
Heating oil — diesel purchases	⁽⁴⁾	$	(22,281	)	$	(2,906	)	$	—
Heating oil — fuel surcharges	⁽⁴⁾	$	(2,209	)	$	—		$	—

____________________________________________________________

Location in statement of operations:

(1) — Revenues

(2) — Cost of sales

(3) — Change in fair value of coal derivatives and coal trading activities, net

(4) — Other operating income, net

- Definition

Tabular disclosure of the location and amount of gains and losses reported in the statement of financial performance, or when applicable, the statement of financial position. For example, (a) gains and losses recognized in the income statement on derivative instruments designated and qualifying as hedging instruments in fair value hedges and related hedged items designated and qualifying in fair value hedges and (b) gains and losses initially recognized in other comprehensive income on derivative instruments designated and qualifying as cash flow hedges.

+ References + Details

Inventories (Tables)

12 Months Ended

Dec. 31, 2012

Inventory Disclosure [Abstract]

Inventories

Inventories consist of the following:



	December 31
	2012		2011
	(In thousands)
Coal	$	180,917	$	206,517
Repair parts and supplies	172,139		163,527
Work-in-process	12,368		7,446
	$	365,424	$	377,490

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2012

Fair Value Disclosures [Abstract]

Summary Of Financial Assets And Liabilities Accounted For At Fair Value

The table below sets forth, by level, the Company’s financial assets and liabilities that are recorded at fair value in the accompanying consolidated balance sheet:



	Fair Value at December 31, 2012
	Total		Level 1		Level 2		Level 3
	(In thousands)
Assets:
Investments in marketable securities	$	239,652	$	103,439	$	136,213	$	—
Derivatives	32,315		22,465		510		9,340
Total assets	$	271,967	$	125,904	$	136,723	$	9,340
Liabilities:
Derivatives	$	1,737	$	—	$	571	$	1,166

Summary Of Change In The Fair Values Of Financial Instruments Categorized As Level 3

The following table summarizes the change in the fair values of financial instruments categorized as level 3.



	Year Ended December 31, 2012
Balance, beginning of period	$	6,211
Realized and unrealized losses recognized in earnings, net	(13,399		)
Realized and unrealized losses recognized in other comprehensive income, net	—
Purchases	17,312
Issuances	—
Settlements	(1,950		)
Ending balance	$	8,174

- Definition

Tabular disclosure of the fair value measurement of assets using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes during the period attributable to the following: (1) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets) and gains or losses recognized in other comprehensive income (loss), and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (2) purchases, sales, issues, and settlements (each type disclosed separately); and (3) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs), by class of asset.

+ References + Details

Accrued Expenses and Other Current Liabilities Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2012

Accrued Expenses and Other Current Liabilities [Abstract]

Schedule of Accrued Liabilities [Table Text Block]

Accrued expenses and other current liabilities consist of the following:



	December 31
	2012		2011
	(In thousands)
Payroll and employee benefits	$	72,405	$	65,323
Taxes other than income taxes	121,029		133,331
Interest	42,413		55,266
Acquired sales contracts (See Note 4)	14,038		38,441
Workers’ compensation (See Note 17)	10,371		11,666
Asset retirement obligations (See Note 14)	38,920		27,119
Other	18,842		17,061
	$	318,018	$	348,207

Taxes Taxes (Tables)

12 Months Ended

Dec. 31, 2012

Taxes [Abstract]

Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]

Significant components of the provision for (benefit from) income taxes are as follows:



	Year Ended December 31
	2012			2011			2010
	(In thousands)
Current:
Federal	$	(20,022	)	$	(20,164	)	$	34,304
State	575			1,212			2,283
Total current	(19,447		)	(18,952		)	36,587
Deferred:
Federal	(322,104		)	13,214			(18,506		)
State	7,834			(1,851		)	(367		)
Total deferred	(314,270		)	11,363			(18,873		)
	$	(333,717	)	$	(7,589	)	$	17,714

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

A reconciliation of the statutory federal income tax provision (benefit) at the statutory rate to the actual provision for (benefit from) income taxes follows:



	Year Ended December 31
	2012			2011			2010
	(In thousands)
Income tax provision (benefit) at statutory rate	$	(356,185	)	$	46,933		$	61,800
Percentage depletion allowance	(40,698		)	(61,971		)	(49,152		)
Goodwill	56,916			—			—
State taxes, net of effect of federal taxes	(23,423		)	(3,055		)	2,299
Change in valuation allowance	31,832			2,416			(383		)
Other, net	(2,159		)	8,088			3,150
	$	(333,717	)	$	(7,589	)	$	17,714

In 2012, 2011 and 2010, compensatory stock opt

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]



	December 31
	2012			2011
	(In thousands)
Deferred tax assets:
Net operating loss carryforwards	$	496,330		$	324,393
Alternative minimum tax credit carryforwards	150,014			151,404
Reclamation and mine closure	104,570			93,914
Goodwill	43,839			—
Acquired sales contracts	38,735			44,717
Workers' compensation	32,241			26,266
Retiree benefit plans	32,087			24,456
Other, primarily accrued liabilities	113,777			120,993
Gross deferred tax assets	1,011,593			786,143
Valuation allowance	(34,663		)	(2,831		)
Total deferred tax assets	976,930			783,312
Deferred tax liabilities:
Plant and equipment	1,411,446			1,566,769
Deferred development	77,013			67,728
Investment in tax partnerships	72,513			66,502
Other	12,780			17,015
Total deferred tax liabilities	1,573,752			1,718,014
Net deferred tax asset (liability)	(596,822		)	(934,702		)
Current asset (liability)	67,360			42,051
Non-current deferred tax asset (liability)	$	(664,182	)	$	(976,753	)

Summary of Income Tax Contingencies [Table Text Block]

A reconciliation of the beginning and ending amounts of gross unrecognized tax benefits follows:



	(In thousands)
Balance at January 1, 2010	$	6,670
Additions based on tax positions related to the current year	1,493
Additions for tax positions of prior years	85
Reductions for tax positions of prior years	(3,830		)
Balance at December 31, 2010	4,418
Additions based on tax positions related to the current year	1,626
Additions for tax positions of prior years	2,754
Balance at December 31, 2011	8,798
Additions based on tax positions related to the current year	409
Additions for tax positions of prior years	21,943
Balance at December 31, 2012	$	31,150

If recognized, the e

- Definition

Tabular disclosure of tax positions taken in the tax returns filed or to be filed for which it is more likely than not that the tax position will not be sustained upon examination by taxing authorities (i.e., uncertain tax positions) and other types of income tax contingencies, including: (1) the policy on classification of interest and penalties; (2) a tabular reconciliation of the total amounts of unrecognized tax benefits at the beginning and end of the period; the total amount(s) of: (3) unrecognized tax benefits that, if recognized, would affect the effective tax rate, and (4) interest and penalties recognized in each of the income statement and balance sheet; (5) for positions for which it is reasonably possible that the total amounts unrecognized will significantly change within 12 months of the reporting date the: (i) nature of the uncertainty, (ii) nature of the event that could occur that would cause the change, and (iii) an estimate of the range of the reasonably possible change or a statement that an estimate of the range cannot be made; and (6) a description of tax years that remain subject to examination by major tax jurisdictions.

+ References + Details

Asset Retirement Obligations Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2012

Asset Retirement Obligations [Abstract]

Schedule of Change in Asset Retirement Obligation [Table Text Block]

The following table describes the changes to the Company's asset retirement obligation liability:



	Year Ended December 31
	2012			2011
	(In thousands)
Balance at January 1 (including current portion)	$	473,903		$	343,119
Accretion expense	39,020			33,601
Obligations incurred or acquired	—			115,019
Adjustments to the liability from changes in estimates	4,400			11,176
Liabilities settled	(68,698		)	(29,012		)
Balance at December 31	$	448,625		$	473,903
Current portion included in accrued expenses	(38,920		)	(27,119		)
Noncurrent liability	$	409,705		$	446,784

Stock-Based Compensation And Other Incentive Plans Stock-Based Compensation And Other Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2012

Stock Based Compensation And Other Incentive Plans [Abstract]

Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]

Information regarding stock option activity under the Incentive Plan follows for the year ended December 31, 2012:



			Weighted Average		Aggregate		Average
	Common		Exercise		Intrinsic		Contract
	Shares		Price		Value		Life
	(In thousands)		(In thousands)		(In thousands)
Options outstanding at January 1	4,953		$	26.72
Granted	1,311		13.28
Exercised	(527	)	9.79
Canceled	(73	)	31.17
Expired	(449	)	13.89
Options outstanding at December 31	5,215		25.99		$	4	6.67
Options exercisable at December 31	2,847		32.26		—		5.40

Schedule of Nonvested Share Activity [Table Text Block]

Information regarding changes in stock options outstanding and not yet vested and the related grant-date fair value under the Incentive Plan follows for the year ended December 31, 2012:



		Weighted Average
	Common Shares	Grant-Date Fair Value
	(In thousands)
Unvested options at January 1	1,796	$	10.96
Granted	1,311	5.27
Vested	(721)	11.13
Canceled	(17)	9.81
Unvested options at December 31	2,369	7.77

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

Weighted average assumptions used in the Black-Scholes option pricing model for granted options follow:



	Year Ended December 31
	2012		2011		2010
Weighted average grant-date fair value per share of options granted	$	5.27	$	14.18	$	9.43
Assumptions (weighted average):
Risk-free interest rate	0.76%		1.92%		2.16%
Expected dividend yield	2.92%		1.25%		1.99%
Expected volatility	60.72%		57.4%		57.1%
Expected life (in years)	4.5		4.5		4.5

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]

Information regarding restricted stock and restricted stock unit activity and weighted average grant-date fair value follows for the year ended December 31, 2012:



	Restricted Stock				Restricted Stock Units
			Weighted Average				Weighted Average
	Common		Grant-Date		Common		Grant-Date
	Shares		Fair Value		Shares		Fair Value
	(In thousands)				(In thousands)
Outstanding at January 1	182		$	26.68	27		$	52.69
Granted	22		13.44		547		13.31
Vested	(10	)	22.89		(27	)	52.69
Canceled	(6	)	32.49		(36	)	13.93
Outstanding at December 31	188		25.14		511		13.26

Accrued Workers' Compensation (Tables)

12 Months Ended

Dec. 31, 2012

Workers' Compensation Expense [Abstract]

Schedule of Changes in Projected Benefit Obligations

The reconciliation of changes in the benefit obligation of the occupational disease liability is as follows:



	December 31
	2012			2011
	(In thousands)
Beginning of year obligation	$	54,184		$	17,412
Service cost	1,993			2,059
Interest cost	2,400			1,799
Actuarial loss (gain)	(5,373		)	7,081
Benefit and administrative payments	(1,873		)	(1,097		)
Curtailments	7,100			—
Acquisition of ICG	—			26,930
Net obligation at end of year	$	58,431		$	54,184

Scheudle of Occupational Disease Obligation

The following table provides the assumptions used to determine the projected occupational disease obligation:



	Year Ended December 31
	2012		2011		2010
Weighted average assumptions:
Discount rate	4.54	%	5.10	%	5.96	%
Cost escalation rate	3.00	%	3.00	%	3.00	%

Schedule of Amounts Recognized in Balance Sheet

Summarized below is information about the amounts recognized in the accompanying consolidated balance sheets for workers' compensation benefits:



	December 31
	2012		2011
	(In thousands)
Occupational disease costs	$	58,431	$	54,184
Traumatic and other workers' compensation claims	33,569		29,430
Total obligations	92,000		83,614
Less amount included in accrued expenses	10,371		11,666
Noncurrent obligations	$	81,629	$	71,948

Workers' Compensation Expense



	Year Ended December 31
	2012			2011			2010
	(In thousands)
Self-insured occupational disease benefits:
Service cost	$	1,993		$	2,059		$	727
Interest cost	2,400			1,799			675
Net amortization	(453		)	(493		)	(1,860		)
Curtailments	3,022			—			—
Total occupational disease	6,962			3,365			(458		)
Traumatic injury claims and assessments	26,565			16,979			9,263
Total workers’ compensation expense	$	33,527		$	20,344		$	8,805

Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2012

Pension and Other Postretirement Benefit Expense [Abstract]

Schedule of Expected Benefit Payments [Table Text Block]

The following represents expected future benefit payments from the plan, which reflect expected future service, as appropriate:



			Other
	Pension		Postretirement
	Benefits		Benefits
	(In thousands)
2013	$	21,275	$	3,987
2014	23,674		4,204
2015	24,210		4,430
2016	28,464		4,720
2017	32,124		4,893
Years 2018-2022	190,016		24,895
	$	319,763	$	47,129

Schedule of Allocation of Plan Assets [Table Text Block]

The Company's pension plan assets at December 31, 2012 and 2011, respectively, are categorized below according to the fair value hierarchy as defined in Note 11, "Fair Value Measurements":



	Total				Level 1				Level 2				Level 3
	2012		2011		2012		2011		2012		2011		2012		2011
	(In thousands)
Equity Securities:^(A)
U.S. small-cap	$	13,099	$	11,178	$	13,099	$	11,178	$	—	$	—	$	—	$	—
U.S. mid-cap	43,946		50,264		12,717		23,474		31,229		26,790		—		—
U.S. large-cap	102,922		91,561		48,536		44,820		54,386		46,741		—		—
Non-U.S.	27,251		22,509		—		—		27,251		22,509		—		—
Fixed income securities:
U.S. government securities^(B)	24,202		13,454		23,483		12,738		719		716		—		—
Non-U.S. government securities^(C)	3,681		2,968		—		—		3,681		2,968		—		—
U.S. government asset and mortgage backed securities^(D)	781		800		—		—		781		800		—		—
Corporate fixed income^(E)	14,016		14,004		—		—		14,016		14,004		—		—
State and local government securities^(F)	9,903		18,416		—		—		9,903		18,416		—		—
Other fixed income^(G)	61,765		51,470		—		—		61,765		51,470		—		—
Short-term investments^(H)	20,894		8,029		—		—		20,894		8,029		—		—
Other investments^(I)	414		421		—		—		414		421		—		—
Total	$	322,874	$	285,074	$	97,835	$	92,210	$	225,039	$	192,864	$	—	$	—

(B) U.S. government securities includes agency and treasury debt. These investments are valued using dealer quotes in an active market.

(G) Other fixed income investments are actively managed fixed income vehicles that are valued at the net asset value per share multiplied by the number of shares held as of the measurement date.

Pension Benefit Costs

Summaries of the changes in the benefit obligations, plan assets and funded status of the plans are as follows:



							Other Postretirement
	Pension Benefits						Benefits
	2012			2011			2012			2011
	(In thousands)
CHANGE IN BENEFIT OBLIGATIONS
Benefit obligations at January 1	$	333,951		$	297,707		$	45,129		$	39,633
Service cost	27,466			16,490			2,142			3,917
Interest cost	15,668			16,253			2,020			3,279
Plan amendments	—			(3,235		)	2,183			(55,542		)
Benefits paid	(23,624		)	(18,848		)	(4,244		)	(1,669		)
Curtailments	(687		)	—			(708		)	—
Acquisition of ICG	—			—			—			48,441
Other-primarily actuarial loss (gain)	38,120			25,584			2,804			7,070
Benefit obligations at December 31	$	390,894		$	333,951		$	49,326		$	45,129
CHANGE IN PLAN ASSETS
Value of plan assets at January 1	$	285,074		$	247,713		$	—		$	—
Actual return on plan assets	42,396			9,443			—			—
Employer contributions	19,028			46,766			4,244			1,669
Benefits paid	(23,624		)	(18,848		)	(4,244		)	(1,669		)
Value of plan assets at December 31	$	322,874		$	285,074		$	—		$	—
Accrued benefit cost	(68,020		)	(48,877		)	(49,326		)	(45,129		)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit (cost)	$	1,890		$	1,736		$	45,938		$	62,920
Accumulated gain (loss)	(68,915		)	(68,302		)	(1,531		)	1,795
	$	(67,025	)	$	(66,566	)	$	44,407		$	64,715
BALANCE SHEET AMOUNTS
Current liability	$	(390	)	$	(633	)	$	(4,240	)	$	(2,820	)
Noncurrent liability	$	(67,630	)	$	(48,244	)	$	(45,086	)	$	(42,309	)
	$	(68,020	)	$	(48,877	)	$	(49,326	)	$	(45,129	)

The following table details the components of pension benefit costs:



	Pension Benefits									Other Postretirement Benefits
Year Ended December 31,	2012			2011			2010			2012			2011			2010
	(In thousands)
Service cost	$	27,466		$	16,490		$	15,870		$	2,142		$	3,917		$	1,509
Interest cost	15,668			16,253			15,822			2,020			3,279			2,083
Curtailments	324			—			—			(4,049		)	—			—
Expected return on plan assets*	(22,030		)	(21,812		)	(19,392		)	—			—			—
Amortization of prior service cost (credit)	259			(189		)	173			(11,458		)	(2,364		)	(2,364		)
Amortization of other actuarial losses (gains)	14,666			8,748			7,130			(522		)	(3,100		)	(2,918		)
Net benefit cost	$	36,353		$	19,490		$	19,603		$	(11,867	)	$	1,732		$	(1,690	)

*The Company does not fund its other postretirement benefit obligations.

ScheduleOfActuarialPresentValueOfProjectedBenefitObligationsTableTextBlock [Table Text Block]

The following table provides the assumptions used to determine the actuarial present value of projected benefit obligations at December 31.



			Other
	Pension		Postretirement
	Benefits		Benefits
	2012	2011	2012	2011
Weighted average assumptions:
Discount rate	4.13%	4.91%	3.64%	4.52%
Rate of compensation increase	3.39%	3.39%	N/A	N/A

Schedule of Assumptions Used [Table Text Block]

The following table provides the assumptions used to determine net periodic benefit cost for years ended December 31.



	Pension Benefits			Other Postretirement Benefits
	2012	2011	2010	2012	2011	2010
Weighted average assumptions:
Discount rate	4.91%	5.71%	5.97%	4.52%	5.23%	5.67%
Rate of compensation increase	3.39%	3.39%	3.39%	N/A	N/A	N/A
Expected return on plan assets	7.75%	8.50%	8.50%	N/A	N/A	N/A

- Definition

Tabular disclosure of one or more of the entity's defined benefit pension plans or one or more other defined benefit postretirement plans, separately for pension plans and other postretirement benefit plans including the entity's schedule of fair value of plan assets for defined benefit or other postretirement plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e2439-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e2417-114920

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e2410-114920

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=21916443&loc=d3e4179-114921

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 158
-Paragraph 4, 7, 16, 20, 21
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5, 6, 7
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Risk Concentrations Risk Concentratons (Tables)

12 Months Ended

Dec. 31, 2012

Risks Concentrations [Abstract]

Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block]



	December 31, 2012
	(In thousands)
Europe (including Morocco and Turkey)	$	674,754
Asia	203,193
North America	72,542
South America	57,184
Brokered sales	145,438
Total	$	1,153,111

Earnings per Common Share (Tables)

12 Months Ended

Dec. 31, 2012

Earnings Per Share [Abstract]

Earnings per Share

The following table provides the basis for earnings (loss) per share calculations by reconciling basic and diluted weighted average shares outstanding:



	Year Ended December 31
	2012	2011	2010
	(In thousands)
Weighted average shares outstanding:
Basic weighted average shares outstanding	211,381	190,086	162,398
Effect of common stock equivalents under incentive plans	—	819	812
Diluted weighted average shares outstanding	211,381	190,905	163,210

Leases Leases (Tables)

12 Months Ended

Dec. 31, 2012

Leases [Abstract]

Operating Leases of Lessee Disclosure [Table Text Block]

Minimum payments due in future years under these agreements in effect at December 31, 2012 are as follows:



	Operating
	Leases		Royalties
	(In thousands)
2013	$	26,837	$	26,303
2014	25,109		35,954
2015	17,748		37,725
2016	9,708		33,833
2017	7,306		32,690
Thereafter	5,334		147,103
	$	92,042	$	313,608

- Definition

Tabular disclosure of a lessee's leasing arrangements including: (1) the basis on which contingent rental payments are determined, (2) the existence and terms of renewal or purchase options and escalation clauses, (3) restrictions imposed by lease arrangements, such as those concerning dividends, additional debt, and further leasing, (4) rent holidays, rent concessions, or leasehold improvement incentives and unusual provisions or conditions. Disclosure may also include the specific period used to amortize material leasehold improvements made at the inception of the lease or during the lease term. Additionally, for operating leases having initial or remaining noncancelable lease terms in excess of one year: (a) future minimum rental payments required as of the date of the latest balance sheet presented, in the aggregate and for each of the five succeeding fiscal years, (b) the total of minimum rentals to be received in the future under noncancelable subleases as of the date of the latest balance sheet presented, and (c) for all operating leases, rental expense for each period for which an income statement is presented, with separate amounts for minimum rentals, contingent rentals, and sublease rentals. Rental payments under leases with terms of a month or less that were not renewed need not be included.

+ References + Details

Segment Information (Tables)

12 Months Ended

Dec. 31, 2012

Segment Reporting [Abstract]

Schedule Of Operating Segment Results



	PRB			APP			WBIT		Other Operating Segments			Corporate, Other and Eliminations			Consolidated
	(in thousands)
December 31, 2012

Revenues	$	1,524,537		$	1,793,575		$	728,089	$	112,837		$	—		$	4,159,038
Income (loss) from operations	100,679			148,512			144,421		5,145			(1,080,345		)	(681,588		)
Depreciation, depletion and amortization	166,539			271,220			71,696		11,512			4,541			525,508
Amortization of acquired sales contracts, net	(1,987		)	(23,925		)	—		723			—			(25,189		)
Total assets	1,972,522			3,875,105			658,255		176,032			3,324,863			10,006,777
Capital expenditures	23,410			275,476			58,465		9,928			27,946			395,225

December 31, 2011
Revenues	$	1,646,947		$	1,915,090		$	672,766	$	51,092		$	—		$	4,285,895
Income (loss) from operations	180,730			283,404			119,665		(4,685		)	(165,538		)	413,576
Depreciation, depletion and amortization	171,693			203,759			81,235		7,876			2,024			466,587
Amortization of acquired sales contracts, net	19,458			(39,988		)	—		(1,539		)	—			(22,069		)
Total assets	2,307,783			4,740,723			681,393		581,040			1,903,020			10,213,959
Capital expenditures	110,999			217,435			66,356		28,243			117,903			540,936

December 31, 2010
Revenues	$	1,606,236		$	1,042,490		$	537,542	$	—		$	—		$	3,186,268
Income (loss) from operations	146,555			193,943			58,082		—			(74,596		)	323,984
Depreciation, depletion and amortization	185,218			97,764			80,497		—			1,587			365,066
Amortization of acquired sales contracts, net	35,606			—			—		—			—			35,606
Total assets	2,295,786			706,624			677,611		—			1,200,748			4,880,769
Capital expenditures	38,142			70,839			65,470		—			140,206			314,657

Reconciliation Statement Of Segment Income From Operations To Consolidated Income Before Income Taxes

A reconciliation of segment income from operations to consolidated income before income taxes follows:



		December 31
		2012			2011			2010
	(In thousands)
Income (loss) from operations		$	(681,588	)	$	413,576		$	323,984
Interest expense		(317,626		)	(230,186		)	(142,549		)
Interest income		5,478			3,309			2,449
Other nonoperating expense		(23,668		)	(51,448		)	(6,776		)
Income (loss) before income taxes		$	(1,017,404	)	$	135,251		$	177,108

- Definition

Tabular disclosure of the profit or loss and total assets for each reportable segment. An entity discloses certain information on each reportable segment if the amounts (a) are included in the measure of segment profit or loss reviewed by the chief operating decision maker or (b) are otherwise regularly provided to the chief operating decision maker, even if not included in that measure of segment profit or loss.

+ References + Details

Quarterly Financial Information Quarterly Financial Information (Tables)

12 Months Ended

Dec. 31, 2012

Quarterly Financial Information [Abstract]

Schedule of Quarterly Financial Information [Table Text Block]

Quarterly financial data for the years ended December 31, 2012 and 2011 is summarized below:



	March 31		June 30			September 30			December 31
			(a)(b)			(a)			(b)
	(In thousands, except per share data)
2012:
Revenues	$	1,039,651	$	1,063,538		$	1,087,618		$	968,231
Gross profit	63,704		54,984			69,249			37,176
Mine closure and asset impairment costs	—		525,762			(2,194		)	—
Goodwill and other intangible asset impairment	—		115,791			—			230,632
Income from operations	54,081		(588,984		)	135,960			(282,645		)
Net income (loss)	1,409		(435,424		)	45,751			(295,423		)
Basic earnings (loss) per common share	$	0.01	$	(2.05	)	$	0.22		$	(1.39	)
Diluted earnings (loss) per common share	$	0.01	$	(2.05	)	$	0.22		$	(1.39	)



	March 31		June 30		September 30		December 31
			(c)		(c)		(c)
	(In thousands, except per share data)
2011:
Revenues	$	872,938	$	985,528	$	1,198,673	$	1,228,756
Gross profit	130,523		172,234		120,085		154,388
Income from operations	102,238		95,354		76,256		139,728
Net income	55,874		6,630		9,121		71,215
Basic earnings per common share	$	0.34	$	0.04	$	0.04	$	0.34
Diluted earnings per common share	$	0.34	$	0.04	$	0.04	$	0.33

Supplemental Condensed Consolidating Financial Information (Tables)

12 Months Ended

Dec. 31, 2012

Supplemental Condensed Consolidating Financial Information [Abstract]

Schedule of Condensed Consolidating Statements of Income [Table Text Block]

Condensed Consolidating Statements of Operations

Year Ended December 31, 2012



	Parent/Issuer			Guarantor Subsidiaries			Non- Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Revenues	$	—		$	4,159,038		$	—		$	—		$	4,159,038
Costs, expenses and other
Cost of sales	10,918			3,427,095			—			—			3,438,013
Depreciation, depletion and amortization	5,392			520,083			33			—			525,508
Amortization of acquired sales contracts, net	—			(25,189		)	—			—			(25,189		)
Change in fair value of coal derivatives and coal trading activities, net	—			(16,590		)	—			—			(16,590		)
Coal derivative settlements, non-hedging	—			(43,990		)	—			—			(43,990		)
Selling, general and administrative expenses	84,198			41,316			8,785			—			134,299
Contract settlement resulting from Patriot Coal bankruptcy	—			58,335			—			—			58,335
Legal contingencies	—			(79,532		)	—			—			(79,532		)
Mine closure and asset impairment costs	—			523,568			—			—			523,568
Goodwill and other intangible asset impairment	—			346,423			—			—			346,423
Other operating income, net	(13,391		)	9,559			(16,387		)	—			(20,219		)
	87,117			4,761,078			(7,569		)	—			4,840,626
Income from investment in subsidiaries	(569,795		)	—			—			569,795			—
Income (loss) from operations	(656,912		)	(602,040		)	7,569			569,795			(681,588		)
Interest expense, net:
Interest expense	(366,614		)	(35,207		)	(3,221		)	87,416			(317,626		)
Interest income	28,097			57,303			7,494			(87,416		)	5,478
	(338,517		)	22,096			4,273			—			(312,148		)
Other nonoperating expense
Net loss resulting from early retirement and refinancing of debt	(21,975		)	(1,693		)	—			—			(23,668		)
Bridge financing costs related to ICG	—			—			—			—			—
	(21,975		)	(1,693		)	—			—			(23,668		)
Income (loss) before income taxes	(1,017,404		)	(581,637		)	11,842			569,795			(1,017,404		)
Provision for (benefit from) income taxes	(333,717		)	—			—			—			(333,717		)
Net income (loss)	(683,687		)	(581,637		)	11,842			569,795			(683,687		)
Less: Net income attributable to noncontrolling interest	(268		)	—			—			—			(268		)
Net income (loss) attributable to Arch Coal, Inc.	$	(683,955	)	$	(581,637	)	$	11,842		$	569,795		$	(683,955	)
Total comprehensive income (loss)	$	(692,239	)	$	(587,616	)	$	11,842		$	575,774		$	(692,239	)

Condensed Consolidating Statements of Operations

Year Ended December 31, 2011



	Parent/Issuer			Guarantor Subsidiaries			Non- Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Revenues	$	—		$	4,285,895		$	—		$	—		$	4,285,895
Costs, expenses and other
Cost of sales	22,926			3,244,984			—			—			3,267,910
Depreciation, depletion and amortization	2,876			463,711						—			466,587
Amortization of acquired sales contracts, net	—			(22,069		)	—			—			(22,069		)
Change in fair value of coal derivatives and coal trading activities, net	—			(2,907		)	—			—			(2,907		)
Coal derivative settlements, non-hedging	—			7			—			—			7
Selling, general and administrative expenses	74,589			40,940			3,527			—			119,056
Mine closure and asset impairment costs	7,316			—			—			—			7,316
Acquisition and transition costs	47,360			—			—			—			47,360
Other operating income, net	(23,306		)	12,615			(250		)	—			(10,941		)
	131,761			3,737,281			3,277			—			3,872,319
Income from investment in subsidiaries	556,442			—			—			(556,442		)	—
Income (loss) from operations	424,681			548,614			(3,277		)	(556,442		)	413,576
Interest expense, net:
Interest expense	(256,221		)	(46,565		)	(2,224		)	74,824			(230,186		)
Interest income	16,281			55,072			6,780			(74,824		)	3,309
	(239,940		)	8,507			4,556			—			(226,877		)
Other nonoperating expense
Net loss resulting from early retirement and refinancing of debt	—			(1,958		)	—			—			(1,958		)
Bridge financing costs related to ICG	(49,490		)	—			—			—			(49,490		)
	(49,490		)	(1,958		)	—			—			(51,448		)
Income (loss) before income taxes	135,251			555,163			1,279			(556,442		)	135,251
Provision for (benefit from) income taxes	(7,589		)	—			—			—			(7,589		)
Net income (loss)	142,840			555,163			1,279			(556,442		)	142,840
Less: Net income attributable to noncontrolling interest	(1,157		)	—			—			—			(1,157		)
Net income (loss) attributable to Arch Coal, Inc.	$	141,683		$	555,163		$	1,279		$	(556,442	)	$	141,683
Total comprehensive income (loss)	$	141,240		$	552,663		$	1,279		$	(553,942	)	$	141,240

Condensed Consolidating Statements of Operations

Year Ended December 31, 2010



	Parent/Issuer			Guarantor Subsidiaries			Non- Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Revenues	$	—		$	3,186,268		$	—		$	—		$	3,186,268
Costs, expenses and other
Cost of sales	11,523			2,384,289			—			—			2,395,812
Depreciation, depletion and amortization	2,933			362,133			—			—			365,066
Amortization of acquired sales contracts, net	—			35,606			—			—			35,606
Change in fair value of coal derivatives and coal trading activities, net	—			8,924			—			—			8,924
Coal derivative settlements, non-hedging	—			(4,542		)	—			—			(4,542		)
Selling, general and administrative expenses	79,580			36,091			2,506			—			118,177
Gain on Knight Hawk transaction	—			(41,577		)	—			—			(41,577		)
Other operating income, net	(10,258		)	(4,924		)	—			—			(15,182		)
	83,778			2,776,000			2,506			—			2,862,284
Income from investment in subsidiaries	393,363			—			—			(393,363		)	—
Income (loss) from operations	309,585			410,268			(2,506		)	(393,363		)	323,984
Interest expense, net:
Interest expense	(143,606		)	(64,377		)	(2,849		)	68,283			(142,549		)
Interest income	11,129			52,899			6,704			(68,283		)	2,449
	(132,477		)	(11,478		)	3,855			—			(140,100		)
Other nonoperating expense
Net loss resulting from early retirement and refinancing of debt	—			(6,776		)	—			—			(6,776		)
Bridge financing costs related to ICG	—			—			—			—			—
	—			(6,776		)	—			—			(6,776		)
Income (loss) before income taxes	177,108			392,014			1,349			(393,363		)	177,108
Provision for (benefit from) income taxes	17,714			—			—			—			17,714
Net income (loss)	159,394			392,014			1,349			(393,363		)	159,394
Less: Net income attributable to noncontrolling interest	(537		)	—			—			—			(537		)
Net income (loss) attributable to Arch Coal, Inc.	$	158,857		$	392,014		$	1,349		$	(393,363	)	$	158,857
Total comprehensive income (loss)	$	172,885		$	400,664		$	1,349		$	(402,013	)	$	172,885

Schedule of Condensed Consolidating Balance Sheets [Table Text Block]

Condensed Consolidating Balance Sheets

December 31, 2012



	Parent/Issuer			Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Assets
Cash and cash equivalents	$	671,313		$	100,468	$	12,841		$	—		$	784,622
Restricted cash	3,453			—		—			—			3,453
Short term investments	234,305			—		—			—			234,305
Receivables	49,281			40,452		247,171			(4,824		)	332,080
Inventories	—			365,424		—			—			365,424
Other	106,786			86,877		557			—			194,220
Total current assets	1,065,138			593,221		260,569			(4,824		)	1,914,104

Property, plant and equipment, net	27,476			7,309,550		72			—			7,337,098

Investment in subsidiaries	8,254,508			—		—			(8,254,508		)	—
Intercompany receivables	(1,367,739		)	1,600,311		(232,572		)	—			—
Note receivable from Arch Western	675,000			—		—			(675,000		)	—
Other	187,171			568,314		90			—			755,575
Total other assets	7,748,940			2,168,625		(232,482		)	(8,929,508		)	755,575
Total assets	$	8,841,554		$	10,071,396	$	28,159		$	(8,934,332	)	$	10,006,777

Liabilities and Stockholders’ Equity
Accounts payable	$	19,859		$	204,370	$	189		$	—		$	224,418
Accrued expenses and other current liabilities	65,293			259,162		124			(4,824		)	319,755
Current maturities of debt and short-term borrowings	32,054			842		—			—			32,896
Total current liabilities	117,206			464,374		313			(4,824		)	577,069
Long-term debt	5,061,925			23,954		—			—			5,085,879
Note payable to Arch Coal	—			675,000		—			(675,000		)	—
Asset retirement obligations	1,646			408,059		—			—			409,705
Accrued pension benefits	33,456			34,174		—			—			67,630
Accrued postretirement benefits other than pension	13,953			31,133		—			—			45,086
Accrued workers’ compensation	25,323			56,306		—			—			81,629
Deferred income taxes	664,182			—		—			—			664,182
Other noncurrent liabilities	69,296			151,360		374			—			221,030
Total liabilities	5,986,987			1,844,360		687			(679,824		)	7,152,210
Stockholders’ equity	2,854,567			8,227,036		27,472			(8,254,508		)	2,854,567
Total liabilities and stockholders’ equity	$	8,841,554		$	10,071,396	$	28,159		$	(8,934,332	)	$	10,006,777

Condensed Consolidating Balance Sheets

December 31, 2011



	Parent/Issuer			Guarantor Subsidiaries		Non-Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Assets
Cash and cash equivalents	$	61,375		$	75,425	$	1,349		$	—		$	138,149
Restricted cash	10,322			—		—			—			10,322
Short term investments	—			—		—			—			—
Receivables	65,187			27,001		378,608			(1,617		)	469,179
Inventories	—			377,490		—			—			377,490
Other	81,732			105,282		620			—			187,634
Total current assets	218,616			585,198		380,577			(1,617		)	1,182,774

Property, plant and equipment, net	21,241			7,918,816		9,093			—			7,949,150

Investment in subsidiaries	8,813,080			—		—			(8,813,080		)	—
Intercompany receivables	(1,190,342		)	1,448,902		(258,560		)	—			—
Note receivable from Arch Western	225,000			—		—			(225,000		)	—
Other	(85,668		)	1,167,501		202			—			1,082,035
Total other assets	7,762,070			2,616,403		(258,358		)	(9,038,080		)	1,082,035
Total assets	$	8,001,927		$	11,120,417	$	131,312		$	(9,039,697	)	$	10,213,959

Liabilities and Stockholders’ Equity
Accounts payable	$	30,576		$	353,180	$	26		$	—		$	383,782
Accrued expenses and other current liabilities	75,121			282,446		85			(1,617		)	356,035
Current maturities of debt and short-term borrowings	172,564			1,987		106,300			—			280,851
Total current liabilities	278,261			637,613		106,411			(1,617		)	1,020,668
Long-term debt	3,308,674			453,623		—			—			3,762,297
Note payable to Arch Coal	—			225,000		—			(225,000		)	—
Asset retirement obligations	877			445,907		—			—			446,784
Accrued pension benefits	19,198			29,046		—			—			48,244
Accrued postretirement benefits other than pension	13,843			28,466		—			—			42,309
Accrued workers’ compensation	17,272			54,676		—			—			71,948
Deferred income taxes	621,483			355,270		—			—			976,753
Other noncurrent liabilities	152,745			102,553		84			—			255,382
Total liabilities	4,412,353			2,332,154		106,495			(226,617		)	6,624,385
Redeemable noncontrolling interest	11,534			—		—			—			11,534
Stockholders’ equity	3,578,040			8,788,263		24,817			(8,813,080		)	3,578,040
Total liabilities and stockholders’ equity	$	8,001,927		$	11,120,417	$	131,312		$	(9,039,697	)	$	10,213,959

Schedule of Condensed Consolidating Statements of Cash Flows [Table Text Block]

Condensed Consolidating Statements of Cash Flows

Year Ended December 31, 2012



	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$	(571,576	)	$	781,551		$	122,829		$	—		$	332,804
Investing Activities
Change in restricted cash	6,869			—			—			—			6,869
Capital expenditures	(4,424		)	(390,801		)	—			—			(395,225		)
Proceeds from dispositions of property, plant and equipment	—			1,328			21,497			—			22,825
Investments in and advances to affiliates	(6,287		)	(13,134		)	—			1,663			(17,758		)
Purchases of short term investments	(236,862		)	—			—			—			(236,862		)
Proceeds from sales of short term investments	1,754			—			—			—			1,754
Purchase of noncontrolling interest	(17,500		)	—			—			—			(17,500		)
Additions to prepaid royalties	—			(13,269		)	—			—			(13,269		)
Cash provided by (used in) investing activities	(256,450		)	(415,876		)	21,497			1,663			(649,166		)
Financing Activities
Contributions from parent	—			1,663			—			(1,663		)	—
Proceeds from the issuance of senior notes	359,753			—			—			—			359,753
Proceeds from term note issuance	1,633,500			—			—			—			1,633,500
Payments to retire debt	—			(452,934		)	—			—			(452,934		)
Net decrease in borrowings under lines of credit and commercial paper program	(375,000		)	—			(106,300		)	—			(481,300		)
Payments on term note	(7,625		)	—			—			—			(7,625		)
Net payments on other debt	(682		)	—			—			—			(682		)
Debt financing costs	(50,022		)	—			(546		)	—			(50,568		)
Dividends paid	(42,440		)	—			—			—			(42,440		)
Issuance of common stock under incentive plans	5,131			—			—			—			5,131
Transactions with affiliates, net	(84,651		)	110,639			(25,988		)	—			—
Cash provided by (used in) financing activities	1,437,964			(340,632		)	(132,834		)	(1,663		)	962,835
Increase in cash and cash equivalents	609,938			25,043			11,492			—			646,473
Cash and cash equivalents, beginning of period	61,375			75,425			1,349			—			138,149
Cash and cash equivalents, end of period	$	671,313		$	100,468		$	12,841		$	—		$	784,622

Condensed Consolidating Statements of Cash Flows

Year Ended December 31, 2011



	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$	(187,039	)	$	998,082		$	(168,801	)	$	—		$	642,242
Investing Activities
Acquisition of ICG, net of cash acquired	(2,894,339		)	—			—			—			(2,894,339		)
Change in restricted cash	5,167			—			—			—			5,167
Capital expenditures	(12,809		)	(528,021		)	(106		)	—			(540,936		)
Proceeds from dispositions of property, plant and equipment	—			25,887			—			—			25,887
Investments in and advances to affiliates	(633,534		)	(33,553		)	—			605,178			(61,909		)
Additions to prepaid royalties	—			(29,957		)	—			—			(29,957		)
Consideration paid related to prior business acquisition	(829		)	—			—			—			(829		)
Cash provided by (used in) investing activities	(3,536,344		)	(565,644		)	(106		)	605,178			(3,496,916		)
Financing Activities
Contributions from parent	—			605,178			—			(605,178		)	—
Proceeds from the issuance of senior notes	2,000,000			—			—			—			2,000,000
Proceeds from the issuance of common stock, net	1,267,933			—			—			—			1,267,933
Payments to retire debt	—			(605,178		)	—			—			(605,178		)
Net decrease in borrowings under lines of credit and commercial paper program	375,000			(56,904		)	106,300			—			424,396
Net proceeds from other debt	5,334			—			—			—			5,334
Debt financing costs	(114,799		)	(16		)	(8		)	—			(114,823		)
Dividends paid	(80,748		)	—			—			—			(80,748		)
Issuance of common stock under incentive plans	2,316			—			—			—			2,316
Transactions with affiliates, net	316,009			(379,973		)	63,964			—			—
Cash provided by (used in) financing activities	3,771,045			(436,893		)	170,256			(605,178		)	2,899,230
Increase (decrease) in cash and cash equivalents	47,662			(4,455		)	1,349			—			44,556
Cash and cash equivalents, beginning of period	13,713			79,880			—			—			93,593
Cash and cash equivalents, end of period	$	61,375		$	75,425		$	1,349		$	—		$	138,149

Condensed Consolidating Statements of Cash Flows

Year Ended December 31, 2010



	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations		Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$	(230,966	)	$	943,361		$	(15,248	)	$	—	$	697,147
Investing Activities
Capital expenditures	(4,814		)	(309,843		)	—			—		(314,657		)
Proceeds from dispositions of property, plant and equipment	—			330			—			—		330
Investments in and advances to affiliates	(13,821		)	(32,364		)	—			—		(46,185		)
Additions to prepaid royalties	—			(27,355		)	—			—		(27,355		)
Consideration paid related to prior business acquisition	(1,262		)	—			—			—		(1,262		)
Cash used in investing activities	(19,897		)	(369,232		)	—			—		(389,129		)
Financing Activities
Proceeds from the issuance of senior notes	500,000			—			—			—		500,000
Payments to retire debt	—			(505,627		)	—			—		(505,627		)
Net decrease in borrowings under lines of credit and commercial paper program	(120,000		)	7,451			(84,000		)	—		(196,549		)
Net proceeds from other debt	82			—			—			—		82
Debt financing costs	(12,022		)	(390		)	(339		)	—		(12,751		)
Dividends paid	(63,373		)	—			—			—		(63,373		)
Issuance of common stock under incentive plans	1,764			—			—			—		1,764
Contribution from non-controlling interest	891			—			—			—		891
Transactions with affiliates, net	(97,021		)	(2,566		)	99,587			—		—
Cash provided by (used in) financing activities	210,321			(501,132		)	15,248			—		(275,563		)
Increase (decrease) in cash and cash equivalents	(40,542		)	72,997			—			—		32,455
Cash and cash equivalents, beginning of period	54,255			6,883			—			—		61,138
Cash and cash equivalents, end of period	$	13,713		$	79,880		$	—		$	—	$	93,593

Accounting Policies (Narrative) (Details) $ in Thousands	12 Months Ended
Accounting Policies (Narrative) (Details) $ in Thousands	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Apr. 09, 2012
Statutory Accounting Practices
Deferred Finance Costs, Net	$ 101,500	$ 90,500
Deferred Finance Costs, Current, Net	17,300	15,800
Interest Costs Capitalized	$ 15,600
Number of mining complexes operated	15
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners				0.50%
Property, Plant and Equipment, Net	$ 7,337,098	7,949,150
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	216,200
Unrecorded Unconditional Purchase Obligation, Due within Two Years	135,300
Unrecorded Unconditional Purchase Obligation, Due within Three Years	135,100
Unrecorded Unconditional Purchase Obligation, Due within Four Years	102,500
Purchase of noncontrolling interest	$ (17,500)
Exploration and Production Equipment [Member] \| Minimum [Member]
Statutory Accounting Practices
Property, Plant and Equipment, Useful Life	5 years
Exploration and Production Equipment [Member] \| Maximum [Member]
Statutory Accounting Practices
Property, Plant and Equipment, Useful Life	32 years
Building and Building Improvements [Member] \| Minimum [Member]
Statutory Accounting Practices
Property, Plant and Equipment, Useful Life	10 years
Building and Building Improvements [Member] \| Maximum [Member]
Statutory Accounting Practices
Property, Plant and Equipment, Useful Life	30 years
Mining Properties and Mineral Rights [Member]
Statutory Accounting Practices
Property, Plant and Equipment, Net	$ 5,100,000	$ 5,600,000
Capital Addition Purchase Commitments [Member]
Statutory Accounting Practices
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	83,400
Unrecorded Unconditional Purchase Obligation, Due within Two Years	67,300
Unrecorded Unconditional Purchase Obligation, Due within Three Years	60,000
Unrecorded Unconditional Purchase Obligation, Due within Four Years	$ 60,000

Debt (Narrative) (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
Debt (Narrative) (Details) - USD ($)	Dec. 31, 2012	Nov. 20, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Nov. 21, 2012	May 30, 2012	May 16, 2012	Mar. 31, 2012	Dec. 31, 2009
Debt Instrument [Line Items]
Interest Paid			$ 310,241,000	$ 213,697,000	$ 134,866,000
Line of credit facility, maximum borrowing capacity	$ 600,000,000		600,000,000						$ 2,000,000,000
Proceeds from Issuance of Long-term Debt			$ 1,633,500,000
Maximum dividend allowed by credit facility			$ 0.03
Expected aggregate maturities in 2013	34,700,000		$ 34,700,000
Expected aggregate maturities in 2014	20,600,000		20,600,000
Expected aggregate maturities in 2015	20,800,000		20,800,000
Expected aggregate maturities in 2016	620,900,000		620,900,000
Expected aggregate maturities in 2017	21,100,000		21,100,000
Net loss resulting from early retirement of debt and refinancing activities			23,668,000	1,958,000	6,776,000
Deferred finance costs	101,500,000		101,500,000	90,500,000
Payments of Financing Costs			50,568,000	114,823,000	12,751,000
Debt Related Commitment Fees and Debt Issuance Costs				49,490,000
Debt Instrument, Unused Borrowing Capacity, Amount	333,000,000		333,000,000
Cash and cash equivalents	$ 784,622,000		$ 784,622,000	138,149,000	93,593,000					$ 61,138,000
Line of Credit Facility, Covenant Terms			Terms of the Company's credit facilities and leases contain financial and other covenants that limit the ability of the Company to, among other things, acquire, dispose, merge or consolidate assets; incur additional debt; pay dividends and make distributions or repurchase stock; make investments; create liens; issue and sell capital stock of subsidiaries; enter into restrictions affecting the ability of restricted subsidiaries to make distributions, loans or advances to the Company; engage in transactions with affiliates and enter into sale and leaseback transactions. In addition, the covenants require the Company to pledge assets to collateralize the revolving credit and term loan facilities. The assets pledged include equity interests in wholly‑owned subsidiaries, certain real property interests, accounts receivable and inventory of the Company. Failure by the Company to comply with such covenants could result in an event of default, which, if not cured or waived, could have a material adverse effect on the Company.
Term Loan Due 2018 [Member]
Debt Instrument [Line Items]
Long-term Debt						$ 250,000,000		$ 1,400,000,000
6.75% Senior Notes Due 2013 [Member]
Debt Instrument [Line Items]
Stated interest rate	6.75%		6.75%
Amount of debt redeemed			$ 450,000,000
Debt Instrument, Repurchased Face Amount	$ 304,000,000		$ 304,000,000
Debt instrument, repurchase amount							$ 146,000,000	$ 304,800,000
6.75% Senior Notes Due 2013 [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Tender offer, offering price per unit of principal	1,002.50		1,002.50
9.875% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 375,000,000		$ 375,000,000
Debt Instrument Initial Issue Price Percentage Of Face Amount			95.934%
Percentage Of Maximum Redemption Aggregate Principal Amount From Equity Proceeds			35.00%
Frequency of periodic payment			Interest is payable on the 9.875%9.875% Notes annually on June 15 and December 15, beginning on June 15, 2013
Stated interest rate	9.875%		9.875%
9.125% Senior Notes Due 2018 [Member]
Debt Instrument [Line Items]
Interest Paid			$ 5,200,000
9.00% Convertible Senior Notes Due 2012 [Member]
Debt Instrument [Line Items]
Stated interest rate	9.00%		9.00%
Debt assumed in acquisition	$ 1,700,000		$ 1,700,000
Calculated conversion rate			2,392.73414
ICG Debt [Member]
Debt Instrument [Line Items]
Debt assumed in acquisition	54,000,000		54,000,000
Net loss resulting from early retirement of debt and refinancing activities				$ (2,000,000)
6.75% Senior Notes Due 2013 [Member]
Debt Instrument [Line Items]
Amount of debt redeemed			500,000,000
Net loss resulting from early retirement of debt and refinancing activities			(6,800,000)
Redemption Premium On Extinguishment Of Debt			5,600,000
Write off of deferred debt issuance cost			1,100,000		3,300,000
Debt Instrument, Unamortized Premium	$ (800,000)		$ (800,000)		$ 2,100,000
4.00% Convertible Senior Notes Due 2017 [Member]
Debt Instrument [Line Items]
Stated interest rate	4.00%		4.00%
Debt assumed in acquisition	$ 298,500,000		$ 298,500,000
Calculated conversion rate			2,614.6848
4.00% and 9.00% Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Principal Amount Increment For Conversion			1,000
Loans Payable [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	1,642,375,000		$ 1,642,375,000
Debt instrument, maturity period			6 years
Debt instrument, discount (premium), percentage			1.00%
Debt instrument, periodic principal payment	$ 4,125,000	$ 3,500,000
Frequency of periodic payment			Quarterly
Basis spread on variable rate	4.50%		4.50%
Loans Payable [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Stated interest rate	1.25%		1.25%
Line of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 350,000,000		$ 350,000,000			$ 600,000,000
Debt Instrument, Date of First Required Payment			Sep. 30, 2012
Write off of deferred debt issuance cost			$ 23,400,000
Line of Credit [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage			0.75%
Line of Credit [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage			0.50%
8.75% Senior Notes Due 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 600,000,000		$ 600,000,000
Debt Instrument Initial Issue Price Percentage Of Face Amount			97.464%
Frequency of periodic payment			Interest is payable on the notes on February 1 and August 1 of each year.
Stated interest rate	8.75%		8.75%
7.25% Senior Notes Due 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 500,000,000		$ 500,000,000
Percentage Of Maximum Redemption Aggregate Principal Amount From Equity Proceeds			35.00%
Frequency of periodic payment			Interest is payable on the 2020 Notes on April 1 and October 1 of each year
Stated interest rate	0.00%		0.00%
7.00% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 1,000,000,000		$ 1,000,000,000
Stated interest rate	7.00%		7.00%
7.25% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 1,000,000,000		$ 1,000,000,000
Stated interest rate	7.25%		7.25%
2019 and 2021 notes [Member]
Debt Instrument [Line Items]
Percentage Of Maximum Redemption Aggregate Principal Amount From Equity Proceeds			35.00%
Frequency of periodic payment			Interest is payable on the 2019 Notes and 2021 Notes on June 15 and December 15 of each year
Redeemable Between August 1, 2013 And July 31, 2014 [Member] \| 8.75% Senior Notes Due 2016 [Member]
Debt Instrument [Line Items]
Call Premium			104.375%
DebtInstrumentRedemptionPeriod			between August 1, 2013 and July 31, 2014
Redeemable Between August 1, 2014 And July 31, 2015 [Member] \| 8.75% Senior Notes Due 2016 [Member]
Debt Instrument [Line Items]
Call Premium			102.188%
DebtInstrumentRedemptionPeriod			between August 1, 2014 and July 31, 2015
August 1, 2015 and Beyond [Member] \| 8.75% Senior Notes Due 2016 [Member]
Debt Instrument [Line Items]
Call Premium			100.00%
DebtInstrumentRedemptionPeriod			on or after August 1, 2015
Redeemable between October 1, 2015 and September 30, 2016 [Member] \| 7.25% Senior Notes Due 2020 [Member]
Debt Instrument [Line Items]
Call Premium			0.00%
DebtInstrumentRedemptionPeriod			between October 1, 2015 and September 30, 2016
Redeemable between October 1, 2016 and September 30, 2017 [Member] \| 7.25% Senior Notes Due 2020 [Member]
Debt Instrument [Line Items]
Call Premium			102.417%
DebtInstrumentRedemptionPeriod			between October 1, 2016 and September 30, 2017
Redeemable between October 1, 2017 and September 30, 2018 [Member] \| 7.25% Senior Notes Due 2020 [Member]
Debt Instrument [Line Items]
Call Premium			101.208%
DebtInstrumentRedemptionPeriod			between October 1, 2017 and September 30, 2018
Redeemable on or after October 1, 2018 [Member] \| 7.25% Senior Notes Due 2020 [Member]
Debt Instrument [Line Items]
Call Premium			100.00%
DebtInstrumentRedemptionPeriod			on or after October 1, 2018
Prior to October 1, 2013 [Member] \| 7.25% Senior Notes Due 2020 [Member]
Debt Instrument [Line Items]
Call Premium			107.25%
Prior to June 15, 2015 [Member] \| 7.00% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Call Premium			107.00%
DebtInstrumentRedemptionPeriod			prior to June 15, 2015
Prior to June 15, 2016 [Member] \| 7.25% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Call Premium			107.25%
DebtInstrumentRedemptionPeriod			prior to June 15, 2016
Redeemable between June 15, 2015 and June 14, 2016 [Member] \| 7.00% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Call Premium			103.50%
DebtInstrumentRedemptionPeriod			from June 15, 2015 through June 14, 2016
Redeemable between June 15, 2016 and June 14, 2017 [Member] \| 7.00% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Call Premium			101.75%
DebtInstrumentRedemptionPeriod			June 15, 2016 through June 14, 2017
Redeemable between June 15, 2016 and June 14, 2017 [Member] \| 7.25% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Call Premium			103.625%
DebtInstrumentRedemptionPeriod			June 15, 2016 through June 14, 2017
June 15, 2017 and Beyond [Member] \| 7.00% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Call Premium			100.00%
DebtInstrumentRedemptionPeriod			beginning on June 15, 2017
Redeemable between June 15, 2017 and June 14, 2018 [Member] \| 7.25% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Call Premium			102.417%
DebtInstrumentRedemptionPeriod			June 15, 2017 through June 14, 2018
Redeemable between June 15, 2018 and June 14, 2019 [Member] \| 7.25% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Call Premium			101.208%
DebtInstrumentRedemptionPeriod			June 15, 2018 through June 14, 2019
June 15, 2019 and Beyond [Member] \| 7.25% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Call Premium			100.00%
DebtInstrumentRedemptionPeriod			beginning on June 15, 2019
Redeemable between December 15, 2016 and December 14, 2017 [Member] \| 9.875% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Call Premium			104.938%
DebtInstrumentRedemptionPeriod			between December 15, 2016 and December 14, 2017
Redeemable between December 15, 2017 and December 14, 2018 [Member] \| 9.875% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Call Premium			102.469%
DebtInstrumentRedemptionPeriod			between December 15, 2017 and December 14, 2018
December 15, 2018 and beyond [Member] \| 9.875% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Call Premium			100.00%
DebtInstrumentRedemptionPeriod			on or after December 15, 2018
Prior to December 15, 2015 [Member] \| 9.875% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Call Premium			109.875%
Repayment of Debt [Member] \| 9.125% Senior Notes Due 2018 [Member]
Debt Instrument [Line Items]
Subsequent Event, senior notes redeemed			$ 251,400,000

Debt (Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Indebtedness to banks under credit facilities	$ 0	$ 481,300
Other	40,350	21,903
Total	5,118,775	4,043,148
Less current maturities of debt and short-term borrowings	32,896	280,851
Long-term debt	$ 5,085,879	3,762,297
6.75% Senior Notes Due 2013 [Member]
Debt Instrument [Line Items]
Senior notes		450,971
Senior notes interest rate	6.75%
Debt Instrument, Face Amount	$ 450,000
8.75% Senior Notes Due 2016 [Member]
Debt Instrument [Line Items]
Senior notes	$ 590,999	588,974
Senior notes interest rate	8.75%
Debt Instrument, Face Amount	$ 600,000
7.00% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Senior notes	$ 1,000,000	1,000,000
Senior notes interest rate	7.00%
9.875% Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Senior notes	$ 360,042	0
Senior notes interest rate	9.875%
Debt Instrument, Face Amount	$ 375,000
7.25% Senior Notes Due 2020 [Member]
Debt Instrument [Line Items]
Senior notes	$ 500,000	500,000
Senior notes interest rate	7.25%
7.25% Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Senior notes	$ 1,000,000	$ 1,000,000
Senior notes interest rate	7.25%
Loans Payable [Member]
Debt Instrument [Line Items]
Term loan ($1.4 billion face value) due 2018	$ 1,627,384
Debt Instrument, Face Amount	$ 1,642,375
Debt Instrument, Basis Spread on Variable Rate	4.50%

Mine Closure and Asset Impairment Costs (Narrative) (Details) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2012 USD ($)	Sep. 30, 2012 USD ($)	Jun. 30, 2012 USD ($)	Mar. 31, 2012 USD ($)	Dec. 31, 2012 USD ($) mining_complex	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)
Restructuring and Related Activities [Abstract]
Restructuring, Settlement and Impairment Provisions	$ 0	$ (2,194)	$ 525,762	$ 0	$ 523,568	$ 7,316
number of mining complexes temporarily idled \| mining_complex					1
number of mining complexes closed \| mining_complex					4
Long-Lived Assets to be Abandoned, Carrying Value of Asset	$ 51,000				$ 51,000
Curtailments					$ (1,770)
Restructuring and Related Cost, Number of Positions Eliminated					750

- Definition

The amount of decrease that is related to an event that significantly reduces the expected years of future service of present employees or eliminates for a significant number of employees the accrual of defined benefits for some or all of their future services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)(10)
-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Plan Curtailment
-URI http://asc.fasb.org/extlink&oid=6520938

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 30
-Section 15
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=7577095&loc=d3e8001-114927

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 87
-Paragraph 264
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 88
-Paragraph 6
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 106
-Paragraph 518
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Mine Closure and Asset Impairment Costs (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Restructuring and Related Activities [Abstract]
Parts and supplies inventory writedown					$ 2,598
Impairment of property, plant and equipment					95,641
Impairment of coal properties and deferred development costs					403,279
Royalty obligations					11,546
Employee termination benefits					12,274
Curtailments					(1,770)
Mine closure and asset impairment costs	$ 0	$ (2,194)	$ 525,762	$ 0	$ 523,568	$ 7,316

Charge to cost of goods sold that represents the reduction of the carrying amount of inventory, generally attributable to obsolescence or market conditions.

+ References + Details

- Definition

This element represents the payments that the lessee is obligated to make or can be required to make in connection with a property under the terms of an agreement classified as an operating lease, excluding contingent rentals and a guarantee by the lessee of the lessor's debt and the lessee's obligation to pay (apart from the rental payments) executory costs such as insurance, maintenance, and taxes.

+ References + Details

- Definition

The charge against earnings in the period for known and estimated costs of termination benefits provided to current employees that are involuntarily terminated under a benefit arrangement associated with exit from or disposal of business activities or restructurings pursuant to a duly authorized plan, excluding costs or losses pertaining to an entity newly acquired in a business combination or a discontinued operation as defined by generally accepted accounting principles and costs associated with one-time termination benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 5.P.4(b))
-URI http://asc.fasb.org/extlink&oid=6394695&loc=d3e140904-122747

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)(10)
-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 5.P.3)
-URI http://asc.fasb.org/extlink&oid=6394695&loc=d3e140864-122747

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5-8
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 5
-Section P
-Subsection 3, 4

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 146
-Paragraph 8-13, 20
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS146-1
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 112
-Paragraph 7
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Acquired Sales Contracts Acquired Sales Contracts (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Supply Commitment [Line Items]
Impairment of Intangible Assets, Finite-lived	$ 15,700
Acquired fair value, Assets	131,819	$ 149,457
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	8,100
Finite-Lived Intangible Assets, Amortization Expense, Year Two	11,600
Finite-Lived Intangible Assets, Amortization Expense, Year Three	10,800
Finite-Lived Intangible Assets, Amortization Expense, Year Four	9,300
Finite-Lived Intangible Assets, Amortization Expense, Year Five	3,200
imparment of intangible asset [Member]
Supply Commitment [Line Items]
Acquired fair value, Assets	$ 17,500

Acquired Sales Contracts Acquired Sales Contracts (Schedule of Acquired Sales Contracts) (Details) - USD ($) $ in Thousands	Dec. 31, 2012	Dec. 31, 2011
Acquired Finite-Lived Intangible Assets And Liabilities By Major Class [Line Items]
Acquired fair value, Assets	$ 131,819	$ 149,457
Acquired fair value, Liabilities	166,697	166,697
Accumulated amortization, Asset	(123,776)	(115,322)
Accumulated amortization, Liabilities	(105,237)	(69,699)
Total, Assets	8,043	34,135
Total, Liabilities	61,460	96,998
Net total, Liabilites	(53,417)	(62,863)
Coal Supply Agreement, Liabilities	14,038	38,441
Other Current Assets [Member]
Acquired Finite-Lived Intangible Assets And Liabilities By Major Class [Line Items]
Coal supply agreement, Assets	5,651	18,929
Accrued Liabilities [Member]
Acquired Finite-Lived Intangible Assets And Liabilities By Major Class [Line Items]
Coal Supply Agreement, Liabilities	14,038	38,441
Other Assets [Member]
Acquired Finite-Lived Intangible Assets And Liabilities By Major Class [Line Items]
Coal supply agreement, Assets	2,392	15,206
Other Noncurrent Liabilities [Member]
Acquired Finite-Lived Intangible Assets And Liabilities By Major Class [Line Items]
Coal Supply Agreement, Liabilities	$ 47,422	$ 58,557

Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPortionAttributableToParent	$ 2,244	$ (4,729)	$ 2,921	$ 1,186
Derivative instruments, before tax	10,895	(11,951)	2,711
Derivative instruments, tax effect	(3,922)	4,301	(976)
OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPortionAttributableToParent	2,244	(4,729)	2,921	1,186
OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent	(18,286)	(4,676)	(10,679)	(20,539)
Pension, Postretirement and Other Post-Employment Benefits, before tax	(21,265)	9,345	15,406
Pension, Postretirement and Other Post-Employment Benefits, tax effect	7,655	(3,342)	(5,546)
OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent	(18,286)	(4,676)	(10,679)	(20,539)
OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParent	(465)	1,455	1,341	(500)
Available-for-sale Securities, before tax	(3,000)	176	2,877
Available-for-sale Securities, tax effect	1,080	(62)	(1,036)
OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	(16,507)	(7,950)	(6,417)	(19,853)
Accumulated Other Comprehensive Income (Loss), before tax	(13,370)	(2,430)	20,994
Accumulated Other Comprehensive Income (Loss), tax effect	4,813	897	(7,558)
OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	$ (16,507)	$ (7,950)	$ (6,417)	$ (19,853)

Investments in Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 223,300
Available-for-sale Securities, Amortized Cost Basis	240,382	$ 5,268
Available-for-sale Securities, Gross Unrealized Losses	2,706	4,394
Available-for-sale Securities, Gross Unrealized Losses	(3,436)	(2,122)
Available-for-sale Securities, Fair Value Disclosure	239,652	7,540
Available-for-sale Securities, Debt Securities, Current	234,305
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	146,993
Available-for-sale Securities, Gross Unrealized Losses	2
Available-for-sale Securities, Gross Unrealized Losses	(412)
Available-for-sale Securities, Fair Value Disclosure	146,583
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	88,118
Available-for-sale Securities, Gross Unrealized Losses	0
Available-for-sale Securities, Gross Unrealized Losses	(396)
Available-for-sale Securities, Fair Value Disclosure	87,722
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	5,271	5,268
Available-for-sale Securities, Gross Unrealized Losses	2,704	4,394
Available-for-sale Securities, Gross Unrealized Losses	(2,628)	(2,122)
Available-for-sale Securities, Fair Value Disclosure	5,347	7,540
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Financial Instruments, Owned, Corporate Debt, at Fair Value	87,722
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	146,583
Available-for-sale Securities, Debt Securities, Current	234,305
Other Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Equity Securities	$ 5,347	$ 7,540

Goodwill (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
Goodwill (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Goodwill [Line Items]
Goodwill	$ 265,423				$ 265,423	$ 596,103	$ 114,963	$ 113,701
Goodwill, Impairment Loss	$ 230,632	$ 0	$ 115,791	$ 0	(330,680)
Black Thunder [Member]
Goodwill [Line Items]
Goodwill				$ 115,800
Goodwill, Impairment Loss					115,800
APP [Member]
Goodwill [Line Items]
Goodwill, Impairment Loss					$ 214,900

- Definition

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=14024403&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 45
-Subparagraph e
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 43
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141R
-Paragraph 72
-Subparagraph d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 45
-Subparagraph e
-Clause 1
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141R
-Paragraph 68
-Subparagraph l
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141R
-Paragraph 34
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

Loss recognized during the period that results from the write-down of goodwill after comparing the implied fair value of reporting unit goodwill with the carrying amount of that goodwill. Goodwill is assessed at least annually for impairment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=14024403&loc=d3e13854-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13777-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=14024403&loc=d3e13816-109267

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 141R
-Paragraph 72
-Subparagraph d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 43
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 20
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 45
-Subparagraph e
-Clause 5
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 142
-Paragraph 47
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Goodwill (Schedule of Goodwill) (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Goodwill [Line Items]
Goodwill, Impairment Loss	$ 230,632	$ 0	$ 115,791	$ 0	$ (330,680)
Goodwill [Roll Forward]
Goodwill, Beginning Balance				596,103	596,103	$ 114,963	$ 113,701
Payments for (Proceeds from) Previous Acquisition						829	1,262
Goodwill, Ending Balance	$ 265,423				265,423	596,103	114,963
Black Thunder [Member]
Goodwill [Line Items]
Goodwill, Impairment Loss					$ 115,800
Goodwill [Roll Forward]
Goodwill, Beginning Balance			$ 115,800
Goodwill, Ending Balance				$ 115,800
Parent [Member]
Goodwill [Roll Forward]
Payments for (Proceeds from) Previous Acquisition						829	$ 1,262
ICG [Member]
Goodwill [Roll Forward]
Goodwill, Acquired During Period						$ 480,311

Equity Investments And Membership Interests In Joint Ventures (Narrative) (Details) T in Thousands, $ in Thousands	1 Months Ended		3 Months Ended	12 Months Ended
	Dec. 31, 2010 USD ($)	Jun. 30, 2010 USD ($) T	Jun. 30, 2010 USD ($) T	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	May 31, 2010
Schedule of Equity Method Investments [Line Items]
Gain on Knight Hawk transaction						$ (41,577)
Investments in and Advances to Affiliates, at Fair Value, Gross Additions					43,489	87,405
Future development costs, maximum limit				72,900
Tongue River [Member]
Schedule of Equity Method Investments [Line Items]
Investments in and Advances to Affiliates, at Fair Value, Gross Additions					12,989
Millennium [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest				38.00%
Investments in and Advances to Affiliates, at Fair Value, Gross Additions					25,000
Tenaska [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest				35.00%
Investments in and Advances to Affiliates, at Fair Value, Gross Additions					5,500	9,768
Future development costs, percentage				35.00%
Future development costs, maximum limit				$ 12,500
DTA [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest				21.875%
Investments in and Advances to Affiliates, at Fair Value, Gross Additions
DKRW [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest				24.00%
Investments in and Advances to Affiliates, at Fair Value, Gross Additions
Interest Rate on Note Receivable				15.00%
Knight Hawk [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	49.00%	42.00%	42.00%			49.00%	33.33%
Additional ownership interest		9.00%
Gain on Knight Hawk transaction			$ (41,600)
Investments in and Advances to Affiliates, at Fair Value, Gross Additions	$ 26,600					$ 77,637
Reserves [Member] \| Knight Hawk [Member]
Schedule of Equity Method Investments [Line Items]
Tons of Coal \| T		68,400	68,400
Goods and Services Exchanged for Equity Instrument [Member] \| Knight Hawk [Member]
Schedule of Equity Method Investments [Line Items]
Mineral Properties, Net		$ 12,100	$ 12,100
Tongue River [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest				35.00%

Equity Investments And Membership Interests In Joint Ventures (Schedule Of Equity Method Investments) (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2010	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Equity Method Investments [Line Items]
Revenues		$ 190,661	$ 184,358	$ 172,933
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance		225,605	177,451	87,268
Investments in affiliates			43,489	87,405
Advances to (distributions from) affiliates, net		7,690	(6,646)	(8,375)
Equity in comprehensive income (loss)		8,920	11,311	11,153
Ending Balance	$ 177,451	242,215	225,605	177,451
Notes receivable from investees		43,828	35,810
Knight Hawk [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance		135,225	131,250	49,603
Investments in affiliates	26,600			77,637
Advances to (distributions from) affiliates, net		(7,151)	(16,621)	(12,639)
Equity in comprehensive income (loss)		20,989	20,596	16,649
Ending Balance	131,250	149,063	135,225	131,250
Notes receivable from investees
DKRW [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance		19,715	21,961	23,589
Investments in affiliates
Advances to (distributions from) affiliates, net
Equity in comprehensive income (loss)		(4,200)	(2,246)	(1,628)
Ending Balance	21,961	15,515	19,715	21,961
Notes receivable from investees		38,680	30,751
DTA [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance		16,086	14,472	14,076
Investments in affiliates
Advances to (distributions from) affiliates, net		4,335	6,498	4,264
Equity in comprehensive income (loss)		(4,959)	(4,884)	(3,868)
Ending Balance	14,472	15,462	16,086	14,472
Notes receivable from investees
Tenaska [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance		15,266	9,768
Investments in affiliates			5,500	9,768
Advances to (distributions from) affiliates, net
Equity in comprehensive income (loss)		(2)	(2)
Ending Balance	9,768	15,264	15,266	9,768
Notes receivable from investees		5,148	5,059
Millennium [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance		26,324
Investments in affiliates			25,000
Advances to (distributions from) affiliates, net		8,798	3,477
Equity in comprehensive income (loss)		(2,908)	(2,153)
Ending Balance		32,214	26,324
Notes receivable from investees
Tongue River [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance		12,989
Investments in affiliates			12,989
Advances to (distributions from) affiliates, net		1,708
Equity in comprehensive income (loss)
Ending Balance		14,697	12,989
Notes receivable from investees

Equity Investments And Membership Interests In Joint Ventures Equity Investments And Membership Interests In Joint Ventures (Summarized Financial Information Of Equity Method Investments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Equity Method Investments and Joint Ventures [Abstract]
Revenues	$ 190,661	$ 184,358	$ 172,933
Gross Profit	15,308	19,495	25,203
Income from Operations	8,898	13,180	20,243
Net Income (Loss)	641	6,788	$ 16,015
Current Assets	78,961	94,644
Noncurrent Assets	387,884	331,848
Total Assets	466,845	426,492
Current Liabilities	57,403	51,674
Noncurrent Liabilities	128,489	120,494
Equity	280,690	254,163
Noncontrolling Interest	263	161
Total liabilities and equity	$ 466,845	$ 426,492

Derivatives (Narrative) (Details) number in Millions, gal in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2012 USD ($) gal	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)
Derivative [Line Items]
Gain (Loss) on Components Excluded from Assessment of Price Risk Hedge Effectiveness	$ 8.2
Gain (loss) on components excluded from assessment of price risk hedge effectiveness, net of tax	5.2
Current asset for the right to reclaim cash collateral		$ 12.4
Current liability for the obligation to post cash collateral	16.2
Net unrealized and realized gains (losses) related to trading portfolio	8.3	$ (3.5)	$ 2.1
Gain on derivative contracts designated as hedge instruments in cash flow hedges to be reclassified from OCI into earnings during the next twelve months	$ 2.2
Minimum Purchase [Member]
Derivative [Line Items]
Gallons of diesel fuel purchased annually \| gal	57
Maximum Purchase [Member]
Derivative [Line Items]
Gallons of diesel fuel purchased annually \| gal	67
Year One [Member]
Derivative [Line Items]
Value of trading portfolio realized	$ (1.1)
Year Two [Member]
Derivative [Line Items]
Value of trading portfolio realized	$ 1.5
Heating Oil-Diesel Purchases [Member]
Derivative [Line Items]
Quantities under derivative contracts	60
Heating Oil-Fuel Surchages [Member]
Derivative [Line Items]
Quantities under derivative contracts \| gal	15

Derivatives (Schedule of Price Risk Derivatives) (Details) number in Thousands	Dec. 31, 2012
Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	11,744
Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held	2,670
Year One [Member] \| Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	6,704
Year One [Member] \| Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held	1,410
Year Two [Member] \| Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	4,260
Year Two [Member] \| Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held	1,260
Year Three [Member] \| Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	780
Year Three [Member] \| Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held	0

Derivatives (Disclosure Of Fair Value Of Derivatives) (Details) - USD ($) $ in Thousands	Dec. 31, 2012	Dec. 31, 2011
Derivative [Line Items]
Derivative Assets	$ 54,863	$ 42,263
Derivative Liabilities	(24,285)	(25,962)
Effect of counterparty netting in derivative assets	(22,548)	(18,134)
Effect of counterparty netting in derivative liabilities	22,548	18,134
Net derivative assets as classified in the balance sheet	32,315	24,129
Net derivative liabilities as classified in the balance sheet	(1,737)	(7,828)
Net derivatives as classified in the balance sheet	30,578	16,301
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Assets	3,277	10,106
Derivative Liabilities	(10)
Designated as Hedging Instrument [Member] \| Coal [Member]
Derivative [Line Items]
Derivative Assets	3,277	1,109
Derivative Liabilities	(10)
Designated as Hedging Instrument [Member] \| Heating Oil-Diesel Purchases [Member]
Derivative [Line Items]
Derivative Assets		8,997
Derivative Liabilities
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Assets	51,586	32,157
Derivative Liabilities	(24,275)	(25,962)
Not Designated as Hedging Instrument [Member] \| Coal Held for Trading Purposes [Member]
Derivative [Line Items]
Derivative Assets	17,403	15,505
Derivative Liabilities	(16,933)	(19,927)
Not Designated as Hedging Instrument [Member] \| Coal [Member]
Derivative [Line Items]
Derivative Assets	24,843	14,855
Derivative Liabilities	(7,342)	(6,035)
Not Designated as Hedging Instrument [Member] \| Heating Oil-Diesel Purchases [Member]
Derivative [Line Items]
Derivative Assets	7,379
Derivative Liabilities	0
Not Designated as Hedging Instrument [Member] \| Heating Oil-Fuel Surchages [Member]
Derivative [Line Items]
Derivative Assets	1,961	1,797
Derivative Liabilities

Derivatives (Net Derivatives As Reflected On The Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ 30,578	$ 16,301
Other Current Assets [Member] \| Heating Oil [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	9,340	10,794
Coal Derivative Assets [Member] \| Coal [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	22,975	13,335
Coal Derivative Liabilities [Member] \| Coal [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ (1,737)	$ (7,828)

Derivatives (Effects Of Derivatives On Measures Of Financial Performance) (Details) - USD ($)
$ in Thousands

3 Months Ended

12 Months Ended

15 Months Ended

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2010

Dec. 31, 2012

Derivative Instruments, Gain (Loss) [Line Items]

Gain (Loss) Recognized in OCI (Effective Portion)

$ 5,250

$ 282

$ 4,208

Coal derivative settlements, non-hedging

$ 43,990

$ (7)

4,542

Gains (Losses) Reclassified from OCI into Income (Effective Portion)

2,675

(2,367)

16,438

Coal Purchases [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Gain (Loss) Recognized in OCI (Effective Portion)

(2,440)

5,145

(2,009)

Gains (Losses) Reclassified from OCI into Income (Effective Portion)

(1,202)

Coal Sales [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Gain (Loss) Recognized in OCI (Effective Portion)

7,690

(4,714)

4,923

Gains (Losses) Reclassified from OCI into Income (Effective Portion)

2,675

(1,602)

1,572

Coal [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Unrealized Gain (Loss) on Derivatives

^[1]

8,272

6,438

(10,991)

Coal derivative settlements, non-hedging

^[2]

43,990

(7)

4,542

Heating Oil-Diesel Purchases [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Gain (Loss) Recognized in OCI (Effective Portion)

(149)

1,294

Gains (Losses) Reclassified from OCI into Income (Effective Portion)

$ 0

437

$ 14,866

Realized Gains (Losses)

^[2]

(22,281)

(2,906)

Heating Oil-Fuel Surchages [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Realized Gains (Losses)

^[2]

$ (2,209)

[1]	.
[2]	.

Inventories (Inventories) (Details) - USD ($) $ in Thousands	Dec. 31, 2012	Dec. 31, 2011
Inventory Disclosure [Abstract]
Coal	$ 180,917	$ 206,517
Repair parts and supplies	172,139	163,527
Work-in-process	12,368	7,446
Inventories	365,424	377,490
Allowance for slow-moving and obsolete inventories	$ 13,600	$ 13,100

- Definition

The amount of the valuation account as of the balance sheet date which reduces the carrying amount of inventory to net realizable value; takes into consideration such factors as market value, excessive quantities based on expected sales, technological obsolescence, and shrinkage. May also provide for estimated product returns or price concessions pertaining to product cost.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 5.BB)
-URI http://asc.fasb.org/extlink&oid=6386940&loc=d3e100047-122729

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.6(a))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e24092-122690

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section 35
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6386567&loc=d3e3927-108312

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
-Paragraph 14
-Chapter 4
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
-Paragraph 8, 9, 14
-Chapter 4
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 43
-Section A
-Paragraph 9
-Chapter 3
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 09
-Article 12

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 6
-Subparagraph a
-Article 5

+ Details

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of senior notes and other long-term debt, including amounts classified as current	$ 5,000.0	$ 4,200.0
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net unrealized losses related to level 3 financial instruments	$ 5.4

Fair Value Measurements (Summary Of Change In The Fair Values Of Financial Instruments Categorized As Level 3) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2012 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 6,211
Realized and unrealized losses recognized in earnings, net	(13,399)
Purchases	17,312
Settlements	(1,950)
Ending balance	$ 8,174

Fair Value Measurements (Summary Of Financial Assets And Liabilities Accounted For At Fair Value) (Details) - USD ($) $ in Thousands	Dec. 31, 2012	Dec. 31, 2011
Assets:
Derivatives	$ 32,315	$ 24,129
Investments in equity securities	239,652	7,540
Liabilities:
Derivatives	1,737	$ 7,828
Total assets	271,967
Level 1 [Member]
Assets:
Derivatives	22,465
Investments in equity securities	103,439
Liabilities:
Derivatives
Total assets	125,904
Level 2 [Member]
Assets:
Derivatives	510
Investments in equity securities	136,213
Liabilities:
Derivatives	571
Total assets	136,723
Level 3 [Member]
Assets:
Derivatives	9,340
Investments in equity securities
Liabilities:
Derivatives	1,166
Total assets	$ 9,340

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

+ References + Details

- Definition

Fair values as of the balance sheet date of all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

+ References + Details

- Definition

Fair values as of the balance sheet date of all liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

+ References + Details

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2012	Dec. 31, 2011
Accrued Expenses and Other Current Liabilities [Abstract]
Payroll and employee benefits	$ 72,405	$ 65,323
Taxes other than income taxes	121,029	133,331
Interest	42,413	55,266
Coal supply agreement liability	14,038	38,441
Workers’ compensation	10,371	11,666
Asset retirement obligations	38,920	27,119
Other	18,842	17,061
Accrued Liabilities, Current	$ 318,018	$ 348,207

- Definition

Carrying value as of the balance sheet date of obligations incurred and payable for real and property taxes. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

+ References + Details

- Definition

Carrying value as of the balance sheet date of [accrued] interest payable on all forms of debt, including trade payables, that has been incurred and is unpaid. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

+ References + Details

- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable arising from transactions not otherwise specified in the taxonomy. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

+ References + Details

Taxes Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
Taxes Taxes (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2008
Taxes [Abstract]
Interest and penalties accrued related to unrecognized tax benefits	$ 1,000	$ 800
Operating loss carryforwards	$ 1,300,000			$ 145,100
Operating Loss Carryforwards, Expiration Dates	expire between 2024 and 2032
Tax credit carryforward	$ 150,000
Furture cash tax benefits accrue		800	$ 1,300
Increase (decrease) in valuation allowance	31,800	2,100	(400)
Interest and penalties recognized	200
Stock options and other equity based compensation, tax expense (benefit)	$ 300	$ (400)	$ (800)

Taxes Taxes (Schedule of Components Of Income Tax) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Taxes [Abstract]
Current Federal Tax Expense (Benefit)	$ (20,022)	$ (20,164)	$ 34,304
Current State and Local Tax Expense (Benefit)	575	1,212	2,283
Current Income Tax Expense (Benefit)	(19,447)	(18,952)	36,587
Deferred Federal Income Tax Expense (Benefit)	(322,104)	13,214	(18,506)
Deferred State and Local Income Tax Expense (Benefit)	7,834	(1,851)	(367)
Deferred Income Tax Expense (Benefit)	(314,270)	11,363	(18,873)
Provision for (benefit from) income taxes	$ (333,717)	$ (7,589)	$ 17,714

- Definition

The component of income tax expense for the period representing amounts paid or payable (or refundable) as determined by applying the provisions of enacted federal tax law to the domestic taxable Income or Loss from continuing operations.

+ References

+ Details

- Definition

The component of income tax expense for the period representing amounts of income taxes paid or payable (or refundable) for the period for all income tax obligations as determined by applying the provisions of relevant enacted tax laws to relevant amounts of taxable Income or Loss from continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h))
-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Current Tax Expense (or Benefit)
-URI http://asc.fasb.org/extlink&oid=6509736

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.7)
-URI http://asc.fasb.org/extlink&oid=6889476&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 45
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph h
-Article 4

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 6
-Section I
-Subsection 7

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 289
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

The component of income tax expense for the period representing amounts paid or payable (or refundable) as determined by applying the provisions of enacted state and local tax law to relevant amounts of taxable Income or Loss from continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.7)
-URI http://asc.fasb.org/extlink&oid=6889476&loc=d3e330036-122817

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Current Tax Expense (or Benefit)
-URI http://asc.fasb.org/extlink&oid=6509736

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h))
-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 45
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph h
-Article 4

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 6
-Section I
-Subsection 7

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 289
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

The component of total income tax expense for the period comprised of the increase (decrease) during the period in the entity's domestic deferred tax assets and liabilities attributable to continuing operations as determined by applying the provisions of the federally enacted tax law.

+ References

+ Details

- Definition

The component of income tax expense for the period representing the increase (decrease) in the entity's deferred tax assets and liabilities pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Deferred Tax Expense (or Benefit)
-URI http://asc.fasb.org/extlink&oid=6510177

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h))
-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.7)
-URI http://asc.fasb.org/extlink&oid=6889476&loc=d3e330036-122817

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph h
-Article 4

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 289
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 45
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 6
-Section I
-Subsection 7

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 28
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

The component of total income tax expense for the period comprised of the increase (decrease) in the entity's state and local deferred tax assets and liabilities attributable to continuing operations as determined by applying the provisions of the applicable enacted tax laws.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Deferred Tax Expense (or Benefit)
-URI http://asc.fasb.org/extlink&oid=6510177

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h))
-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.7)
-URI http://asc.fasb.org/extlink&oid=6889476&loc=d3e330036-122817

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 45
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 109
-Paragraph 8, 16, 17, 289
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 6
-Section I
-Subsection 7

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph h
-Article 4

+ Details

Taxes Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Taxes [Abstract]
Income tax expense statutory rate	$ (356,185)	$ 46,933	$ 61,800
Percentage depletion allowance	(40,698)	(61,971)	(49,152)
Income Tax Reconciliation, Nondeductible Expense, Impairment Losses	56,916
State taxes, net of effect of federal taxes	(23,423)	(3,055)	2,299
Change in valuation allowance	31,832	2,416	(383)
Other, net	(2,159)	8,088	3,150
Provision for (benefit from) income taxes	$ (333,717)	$ (7,589)	$ 17,714

Taxes Taxes (Schedule of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2012	Dec. 31, 2011
Taxes [Abstract]
Alternative Minimum Tax Credit Carryforwards	$ 496,330	$ 324,393
Net Operating Loss Carryforwards	150,014	151,404
Reclamation and mine closure	104,570	93,914
Deferred Tax Assets, Goodwill and Intangible Assets	43,839	0
Advance royalties	32,241	26,266
Plant And Equipment	32,087	24,456
Acquired sales contracts	38,735	44,717
Other	113,777	120,993
Gross Deferred Tax Assets	1,011,593	786,143
Valuation Allowance	(34,663)	(2,831)
Total Deferred Tax Assets	976,930	783,312
Deferred Tax Liabilities, Plant And Equipment	1,411,446	1,566,769
Deferred Development	77,013	67,728
Investment in tax partnerships	72,513	66,502
Other	12,780	17,015
Tota Deferred Tax Liabilities	1,573,752	1,718,014
Net Deferred Tax Asset	(596,822)	(934,702)
Current liability	67,360	42,051
Long-term Deferred Tax Asset	$ (664,182)	$ (976,753)

Taxes Taxes (Schedule of Gross Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	$ 8,798	$ 4,418	$ 6,670
Increases Resulting from Current Period Tax Positions	409	1,626	1,493
Increases Resulting from Prior Period Tax Positions	21,943	2,754	85
Decreases Resulting from Prior Period Tax Positions			(3,830)
Ending Balance	$ 31,150	$ 8,798	$ 4,418

Asset Retirement Obligations Asset Retirement Obligations (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
asset retirement obligations [Line Items]
Liabilities settled	$ (68,698)	$ (29,000)
Surety bonds outstanding	262,900
Letters of Credit Outstanding, Amount	18,000
Asset Retirement Obligations [Member]
asset retirement obligations [Line Items]
Self-bonding obligations	$ 388,400

Asset Retirement Obligations Asset Retirement Obligations (Schedule of Asset Retirement Obligations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	$ 473,903	$ 343,119
Accretion expense	39,020	33,601
Obligations incurred or acquired	0	115,019
Adjustments to the liability from changes in estimates	4,400	11,176
Liabilities settled	(68,698)	(29,000)
Ending Balance	448,625	473,903
Current portion included in accrued expenses	(38,920)	(27,119)
Noncurrent liability	$ 409,705	$ 446,784

Capital Stock Capital Stock (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	5 Months Ended	6 Months Ended	12 Months Ended
	Jun. 08, 2011	Jul. 08, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock transactions
Proceeds from the sale of common stock, net				$ 1,267,933
Stock repurchase authorized number			14,000,000
Outstanding shares available for repurchase			10,925,800
ICG [Member]
Stock transactions
Common stock public offering price	$ 27.00
Proceeds from the sale of common stock, net		$ 18,400		$ 1,250,000
Common stock issued	48,000,000			700,000

Stock-Based Compensation And Other Incentive Plans (Narrative) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options compensation expense	$ 8,000	$ 8,800	$ 10,600
Exercised, aggregate intrinsic value	$ 1,800	$ 2,600	$ 3,000
Granted, Common Shares	1,311
Weighted average exercise price of options granted	$ 13.28
Weighted average grant-date fair value per share of options granted	$ 5.27	$ 14.18	$ 9.43
Option, weighted average risk free rate	0.76%	1.92%	2.16%
Option, weighted average dividend yield	2.92%	1.25%	1.99%
Option, weighted average volatility	60.72%	57.40%	57.10%
Expected life of options (Years)	4 years 6 months	4 years 6 months	4 years 6 months
Shares authorized for incentive plan	18,000
Unrecognized compensation cost	$ 7,000
Options vested in period fair value	8,000	$ 9,900	$ 10,600
Long term incentive plan amounts accrued	$ 72,405	65,323
Participans maximum deferred amount in base salaries percentage	85.00%
Participants maximum deferred amount in annual incentive awards percentage	100.00%
Participants maximum deferred stock awards percentage	100.00%
Net cash surrender values	$ 35,400	35,800
Deferred compensation plan liability	31,300	32,700
Net income (expense) related to deferred compensation plan	3,300	6,200	(2,800)
long term incentive plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense	8,100	2,700	$ 3,800
Long term incentive plan amounts accrued	$ 13,100	9,600
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of restricted stock granted	$ 13.31
Grant date fair value	$ 1,400	$ 1,400
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of restricted stock granted	$ 13.44	$ 30.42	$ 22.03
Grant date fair value	$ 200	$ 1,100	$ 400
Restricted Stock And Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	6,900
Restricted compensation expense	$ 3,500	$ 2,100	$ 1,100
Restricted Stock And Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based awards vesting period	3 years
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based awards vesting period	3 years
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based awards vesting period	4 years

Stock-Based Compensation And Other Incentive Plans Stock-Based Compensation And Other Incentive Plans (Schedule Of Stock Option Activity Under Incentive Plan) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock Based Compensation And Other Incentive Plans [Abstract]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price	$ 13.89
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	5,200	2,600	2,500
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	5 years 4 months 24 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 25.99	$ 26.72
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 4
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	6 years 8 months 3 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 32.26
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding at January 1	4,953
Granted, Common Shares	1,311
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 13.28
Exercised, Common Shares	(527)
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$ 9.79
Cancelled, Common Shares	(73)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price	$ 31.17
Expired, Common Shares	(449)
Options outstanding at December 31		4,953
Options exercisable at December 31	2,847

Stock-Based Compensation And Other Incentive Plans Stock Based Compensation And Other Incentive Plans (Changes in Stock Options Outstanding And Not Yet Vested And Related Grant-Date Fair Value Under The Incentive Plan) (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2012 shares
Stock Based Compensation And Other Incentive Plans [Abstract]
Unvested options, Weighted Average Grant-Date Fair Value	10.96
Granted, Weighted Average Grant-Date Fair Value	5.27
Vested, Weighted Average Grant-Date Fair Value	11.13
Canceled, Weighted Average Grant-Date Fair Value	9.81
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding at January 1	1,796
Granted, Common Shares	1,311
Vested, Common Shares	(721)
Cancelled, Common Shares	(17)

Stock-Based Compensation And Other Incentive Plans Stock-Based Compensation And Other Incentive Plans (Schedule of Weighted Average Assumptions Used in Option Pricing) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Stock-Based Compensation [Abstract]
Weighted average grant-date fair value per share of options granted	$ 5.27	$ 14.18	$ 9.43
Option, weighted average risk free rate	0.76%	1.92%	2.16%
Option, weighted average dividend yield	2.92%	1.25%	1.99%
Option, weighted average volatility	60.72%	57.40%	57.10%
Expected life of options (Years)	4 years 6 months	4 years 6 months	4 years 6 months

Stock-Based Compensation And Other Incentive Plans Stock-Based Compensation And Other Incentive Plans (Restricted Stock And Restricted Stock Unit Activity And Weighted Average Grant-Date Fair Value) (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2012 $ / shares shares	Dec. 31, 2011 $ / shares shares	Dec. 31, 2010 $ / shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Canceled, Weighted Average Grant-Date Fair Value	9.81
Restricted Stock [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Outstanding Weighted Average Grant Date Price \| $ / shares	$ 25.14	$ 26.68
Weighted average fair value of restricted stock granted \| $ / shares	13.44	$ 30.42	$ 22.03
Vested, Weighted Average Grant-Date Fair Value \| $ / shares	$ 22.89
Canceled, Weighted Average Grant-Date Fair Value	32.49
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Oustanding as of January 1	182
Shares granted during period	22
Vested	(10)
Canceled	(6)
Outstanding as of December 31	188	182
Restricted Stock Units (RSUs) [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Outstanding Weighted Average Grant Date Price \| $ / shares	$ 13.26	$ 52.69
Weighted average fair value of restricted stock granted \| $ / shares	13.31
Vested, Weighted Average Grant-Date Fair Value \| $ / shares	$ 52.69
Canceled, Weighted Average Grant-Date Fair Value	13.93
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Oustanding as of January 1	27
Shares granted during period	547
Vested	(27)
Canceled	(36)
Outstanding as of December 31	511	27

Accrued Workers' Compensation Accrued Workers' Compensation (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Accrued Workers' Compensation [Abstract]
Surety Bonds And Letters Of Credit Outstanding	$ 61.1
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), Net Gains (Losses), before Tax	4.7	$ 5.5
Defined Benefit Plan, Amortization of Net Gains (Losses)	$ 0.9

- Definition

The pretax net amount of gains and losses that are not yet recognized as a component of net periodic benefit cost, and that are recognized as increases or decreases in other comprehensive income as they arise. Gains and losses are due to changes in the value of either the benefit obligation or the plan assets resulting from experience different from that assumed or from a change in an actuarial assumption, or the consequence of a decision to temporarily deviate from the substantive plan.

+ References + Details

Accrued Workers' Compensation (Worker's Compensation Expense) (Details) - Workers' Compensation [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accrued Workers' Compensation [Line Items]
Service cost	$ 1,993	$ 2,059	$ 727
Interest cost	2,400	1,799	675
Net amortization	(453)	(493)	(1,860)
Recognized Net Gain (Loss) Due to Curtailments	3,022	0	0
Total net benefit	6,962	3,365	(458)
Traumatic injury claims and assessments	26,565	16,979	9,263
Total workers' compensation expense	$ 33,527	$ 20,344	$ 8,805

- Definition

The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

+ References + Details

- Definition

The amount of net gain (loss) recognized in net periodic benefit cost as a result of an event that significantly reduces the expected years of future service of present employees or eliminates for a significant number of employees the accrual of defined benefits for some or all of their future services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Plan Curtailment
-URI http://asc.fasb.org/extlink&oid=6520938

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(7)
-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 30
-Section 15
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=7577095&loc=d3e8001-114927

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph h
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 106
-Paragraph 518
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 87
-Paragraph 264
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 88
-Paragraph 6
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Service Cost (Component of Net Periodic Pension Cost)
-URI http://asc.fasb.org/extlink&oid=6525008

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(1)
-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 87
-Paragraph 264
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 132R
-Paragraph 5
-Subparagraph a, h
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 106
-Paragraph 518
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Accrued Workers' Compensation Accrued Workers' Compensation (Schedule of Changes in Projected Benefit Obligation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at January 1	$ 54,184	$ 17,412
Defined Benefit Plan, Curtailments	(1,770)
Benefit Obligations at December 31		54,184	$ 17,412
Occupational Disease [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at December 31	58,431
Workers' Compensation [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	1,993	2,059	727
Interest cost	2,400	1,799	$ 675
Actuarial Loss	(5,373)	7,081
Benefits Paid	(1,873)	(1,097)
Defined Benefit Plan, Curtailments	7,100
Acquisition of ICG		$ 26,930

Accrued Workers' Compensation Accrued Wokers' Compensation (Schedule of Assumptions Used) (Details) - Workers' Compensation [Member]	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accrued Workers' Compensation [Line Items]
Discount rate	4.54%	5.10%	5.96%
Cost escalation rate	3.00%	3.00%	3.00%

Accrued Workers' Compensation Accrued Workers' Compensation (Schedule Of Amounts Recognized in Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2012	Dec. 31, 2011
Accrued Workers' Compensation [Line Items]
Less amount included in accrued expenses	$ 10,371	$ 11,666
Noncurrent obligations	81,629	71,948
Occupational Disease [Member]
Accrued Workers' Compensation [Line Items]
Occupational disease costs	58,431	54,184
Workers' Compensation [Member]
Accrued Workers' Compensation [Line Items]
Occupational disease costs	33,569	29,430
Total obligations	92,000	83,614
Less amount included in accrued expenses	10,371	11,666
Noncurrent obligations	$ 81,629	$ 71,948

Employee Benefit Plans Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed		7.50%
Accumulated benefit obligation of pension plans		$ 366,100	$ 314,700
Benefit obligation for the unfunded pension plan		10,600
Accumulated benefit obligation for the unfunded pension plan		9,400
Defined Benefit Plan, Amortization of Net Gains (Losses)		$ 900
Ultimate trend rate		4.50%
Effect of one-percentage-point increase in health care cost trend rate		$ 1,000
Effect of one-percentage-point decrease in health care cost trend rate		800
Pension Contributions	$ 900
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of net prior service cost		200
Defined Benefit Plan, Amortization of Net Gains (Losses)		16,200
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Amendments		2,183
Defined Benefit Plan, Effect of Plan Amendment on Accumulated Benefit Obligation			(55,542)
Amortization of net prior service cost		11,000
Defined Benefit Plan, Amortization of Net Gains (Losses)		306
Other Pension Plans, Postretirement or Supplemental Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Other postretirement benefits payments		$ 27,200	$ 25,900	$ 18,100
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations		65.00%
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations		30.00%
Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Target Plan Asset Allocations		5.00%

Employee Benefit Plans (Pension And Other Postretirement Benefit Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Curtailments	$ (1,770)
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	27,466	$ 16,490	$ 15,870
Interest cost	15,668	16,253	15,822
Curtailments	(687)
Expected return on plan assets	(22,030)	(21,812)	(19,392)
Amortization of prior service cost (credit)	259	(189)	173
Amortization of other actuarial (gains) losses	14,666	8,748	7,130
Total net benefit	36,353	19,490	19,603
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	2,142	3,917	1,509
Interest cost	2,020	3,279	2,083
Curtailments	(708)
Expected return on plan assets	0	0	0
Amortization of prior service cost (credit)	(11,458)	(2,364)	(2,364)
Amortization of other actuarial (gains) losses	(522)	(3,100)	(2,918)
Total net benefit	$ (11,867)	$ 1,732	$ (1,690)

Employee Benefit Plans Employee Benefit Plans (Schedule of Defined Benefit Plans Disclosures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Accumulated gain (loss)	$ 4,700	$ 5,500
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at January 1	54,184	17,412
Curtailments	(1,770)
Benefit Obligations at December 31		54,184	$ 17,412
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Value of Plan Assets at January 1	285,074
Value of Plan Assets at December 31	322,874	285,074
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accrued benefit cost	(68,020)	(48,877)
Prior service cost (credit)	1,890	1,736
Accumulated gain (loss)	(68,915)	(68,302)
Total not yet recognized as a component of net periodic benefit cost	(67,025)	(66,566)
Current liability	(390)	(633)
Noncurrent liability	(67,630)	(48,244)
Pension and Other Postretirement Defined Benefit Plans, Liabilities	(68,020)	(48,877)
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at January 1	333,951	297,707
Service cost	27,466	16,490	15,870
Interest cost	15,668	16,253	15,822
Plan Amendments		(3,235)
Benefits Paid	(23,624)	(18,848)
Curtailments	(687)
Acquisition of ICG
Other-primary actuarial loss (gain)	38,120	25,584
Benefit Obligations at December 31	390,894	333,951	297,707
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Value of Plan Assets at January 1	285,074	247,713
Actual Return on Plan Assets	42,396	9,443
Employer contributions	19,028	46,766
Benefits Paid	(23,624)	(18,848)
Value of Plan Assets at December 31	322,874	285,074	247,713
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Accrued benefit cost	(49,326)	(45,129)
Prior service cost (credit)	45,938	62,920
Accumulated gain (loss)	(1,531)	1,795
Total not yet recognized as a component of net periodic benefit cost	44,407	64,715
Current liability	(4,240)	(2,820)
Noncurrent liability	(45,086)	(42,309)
Pension and Other Postretirement Defined Benefit Plans, Liabilities	(49,326)	(45,129)
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at January 1	45,129	39,633
Service cost	2,142	3,917	1,509
Interest cost	2,020	3,279	2,083
Plan Amendments	2,183
Benefits Paid	(4,244)	(1,669)
Curtailments	(708)
Acquisition of ICG		48,441
Other-primary actuarial loss (gain)	2,804	7,070
Benefit Obligations at December 31	49,326	45,129	39,633
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Value of Plan Assets at January 1	0	0
Actual Return on Plan Assets	0	0
Employer contributions	4,244	1,669
Benefits Paid	(4,244)	(1,669)
Value of Plan Assets at December 31	$ 0	0	$ 0
Defined Benefit Plan, Effect of Plan Amendment on Accumulated Benefit Obligation		$ (55,542)

Employee Benefit Plans Employee Benefit Plans (Schedule of Net Benefit Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans, Defined Benefit [Member]
Defined benefit costs [Line Items]
Service cost	$ 27,466	$ 16,490	$ 15,870
Interest cost	15,668	16,253	15,822
Recognized Net Gain (Loss) Due to Curtailments	324		0
Expected return on plan assets	22,030	21,812	19,392
Amortization of prior service cost (credit)	259	(189)	173
Amortization of other actuarial losses (gains)	(14,666)	(8,748)	(7,130)
Total net benefit	36,353	19,490	19,603
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined benefit costs [Line Items]
Service cost	2,142	3,917	1,509
Interest cost	2,020	3,279	2,083
Recognized Net Gain (Loss) Due to Curtailments	(4,049)	0	0
Expected return on plan assets	0	0	0
Amortization of prior service cost (credit)	(11,458)	(2,364)	(2,364)
Amortization of other actuarial losses (gains)	522	3,100	2,918
Total net benefit	$ (11,867)	$ 1,732	$ (1,690)

Employee Benefit Plans Employee Benefit Plans (Schedule of Assumptions Used to Calculate Benefit Obligations) (Details)	Dec. 31, 2012	Dec. 31, 2011
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	4.13%	4.91%
Rate of compensation increase	3.39%	3.39%
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.64%	4.52%

Employee Benefit Plans Employee Benefit Plans (Schedule of Assumptions Used) (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount Rate	4.91%	5.71%	5.97%
Rate of Compensation Increase	3.39%	3.39%	3.39%
Expected return on plan assets	7.75%	8.50%	8.50%
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount Rate	4.52%	5.23%	5.67%

Employee Benefit Plans Employee Benefit Plans (Summary Of Estimated Future Benefit Payments) (Details) $ in Thousands	Dec. 31, 2012 USD ($)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	$ 21,275
Defined Benefit Plan, Expected Future Benefit Payments, Rolling Year Two	23,674
Defined Benefit Plan, Expected Future Benefit Payments, Year Three	24,210
Defined Benefit Plan, Expected Future Benefit Payments, Year Four	28,464
Defined Benefit Plan, Expected Future Benefit Payments, Year Five	32,124
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter	190,016
DefinedBenefitPlanExpectedFutureBenefitPaymentsTotal	319,763
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	3,987
Defined Benefit Plan, Expected Future Benefit Payments, Rolling Year Two	4,204
Defined Benefit Plan, Expected Future Benefit Payments, Year Three	4,430
Defined Benefit Plan, Expected Future Benefit Payments, Year Four	4,720
Defined Benefit Plan, Expected Future Benefit Payments, Year Five	4,893
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter	24,895
DefinedBenefitPlanExpectedFutureBenefitPaymentsTotal	$ 47,129

Risk Concentrations Risk Concentrations (Narrative) (Details) $ in Thousands, T in Millions	12 Months Ended
	Dec. 31, 2012 USD ($) T	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)
Concentration Risk [Line Items]
Sales to customers in foreign countries	$ 1,200,000	$ 920,000	$ 471,500
Tons of coal sold \| T	140.8
Receivables	$ 332,080	469,179
Trade accounts receivable	$ 247,539	380,595
Percentage of tons sold under long term contract	70.00%
Long term contracts percentage of company revenue	50.00%
Long-term contracts, life term, minimum	1 year
Long-term contracts, life term, maximum	8 years
Electric Utilities [Member]
Concentration Risk [Line Items]
Receivables	$ 159,500	$ 261,200
Percentage of total trade accounts receivable	65.00%	69.00%
Domestic And Foreign Steel Producers [Member]
Concentration Risk [Line Items]
Trade accounts receivable	$ 86,600	$ 117,400
Trade receivables, percentage	35.00%	31.00%

Risk Concentrations Rick Concentrations (Schedule of Foreign Revenues) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
foreign revenue [Line Items]
Sales to customers in foreign countries	$ 1,200,000	$ 920,000	$ 471,500
Europe [Member]
foreign revenue [Line Items]
Sales to customers in foreign countries	674,754
South America [Member]
foreign revenue [Line Items]
Sales to customers in foreign countries	57,184
North America [Member]
foreign revenue [Line Items]
Sales to customers in foreign countries	72,542
Asia [Member]
foreign revenue [Line Items]
Sales to customers in foreign countries	203,193
Brokered Sales [Member]
foreign revenue [Line Items]
Sales to customers in foreign countries	145,438
Total [Member]
foreign revenue [Line Items]
Sales to customers in foreign countries	$ 1,153,111

Earnings Per Common Share (Reconciling Schedule of Basic and Diluted Weighted Average Shares Outstanding) (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share [Abstract]
Basic, weighted average shares outstanding	211,381	190,086	162,398
Effect of common stock equivalents under incentive plans	0	819	812
Diluted weighted average shares outstanding	211,381	190,905	163,210

- Definition

The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

+ References + Details

- Definition

Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=7655603&loc=d3e1448-109256

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Weighted-Average Number of Common Shares Outstanding
-URI http://asc.fasb.org/extlink&oid=6528421

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Emerging Issues Task Force (EITF)
-Number 07-4
-Paragraph 4
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 128
-Paragraph 8
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 128
-Paragraph 171
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 128
-Paragraph 40
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Earnings Per Common Share Earnings Per Common Share (Narrative) (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Common Share [Abstract]
Effect of options to purchase common stock	5.2	2.6	2.5

- Definition

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Antidilution
-URI http://asc.fasb.org/extlink&oid=6505113

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Diluted Earnings Per Share
-URI http://asc.fasb.org/extlink&oid=6510752

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Contingent Stock Agreement
-URI http://asc.fasb.org/extlink&oid=6508534

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 128
-Paragraph 40
-Subparagraph c
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 128
-Paragraph 13, 14
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Emerging Issues Task Force (EITF)
-Number 07-4
-Paragraph 4
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 128
-Paragraph 171
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Leases Leases (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Leases Leases (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
lease payments [Line Items]
Surety bonds outstanding	$ 262.9
Rental expense	41.2	$ 43.9	$ 41.6
Royalty expense	302.0	$ 349.0	$ 286.8
lease [Member]
lease payments [Line Items]
Surety bonds outstanding	$ 60.7

Leases Leases (Schedule of Lease Minimum Payments) (Details) $ in Thousands	Dec. 31, 2012 USD ($)
Operating Lease Expense [Member]
lease payments [Line Items]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	$ 26,837
Operating Leases, Future Minimum Payments, Due in Two Years	25,109
Operating Leases, Future Minimum Payments, Due in Three Years	17,748
Operating Leases, Future Minimum Payments, Due in Four Years	9,708
Operating Leases, Future Minimum Payments, Due in Five Years	7,306
Operating Leases, Future Minimum Payments, Due Thereafter	5,334
Operating Leases, Future Minimum Payments Due	92,042
Royalty Agreements [Member]
lease payments [Line Items]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	26,303
Operating Leases, Future Minimum Payments, Due in Two Years	35,954
Operating Leases, Future Minimum Payments, Due in Three Years	37,725
Operating Leases, Future Minimum Payments, Due in Four Years	33,833
Operating Leases, Future Minimum Payments, Due in Five Years	32,690
Operating Leases, Future Minimum Payments, Due Thereafter	147,103
Operating Leases, Future Minimum Payments Due	$ 313,608

Transactions with Patriot Coal Corporation (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Guarantor Obligations [Line Items]
Contract settlement resulting from Patriot Coal bankruptcy	$ (58,335)
Contractual Obligation, Due in Next Twelve Months	7,600
Letters of credit posted in the Company's favor	16,700
Bonding Requirements [Member]
Guarantor Obligations [Line Items]
Guarantee obligations, maximum exposure, undiscounted	$ 34,400

Contingencies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Contingencies (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2012	Dec. 31, 2011	Aug. 25, 2011	Aug. 13, 2007
Purchase replacement coal				$ 100.0
Damages and interest awarded			$ 104.1
Appeal Bond	$ 124.9
Amount accrued	32.8	$ 117.2
Amount accrued current portion	4.4	$ 6.3
Unrecorded Unconditional Purchase Obligation, Due in Next Twelve Months	216.2
Unrecorded Unconditional Purchase Obligation, Due within Two Years	135.3
Unrecorded Unconditional Purchase Obligation, Due within Three Years	135.1
Unrecorded Unconditional Purchase Obligation, Due within Four Years	102.5
Unrecorded Unconditional Purchase Obligation, Due within Five Years	98.6
Unrecorded Unconditional Purchase Obligation, Due after Five Years	445.6
Maximum [Member]
Aggregate amount of past and future damages	377.0
Minimum [Member]
Aggregate amount of past and future damages	$ 228.0

Segment Information (Narrative) (Details)	12 Months Ended
Segment Information (Narrative) (Details)	Dec. 31, 2012 Segment
Segment Reporting [Abstract]
Segment Reporting, Factors Used to Identify Entity's Reportable Segments	3

Segment Information (Schedule Of Operating Segment Results) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Coal Products and Services Revenue	$ 968,231	$ 1,087,618	$ 1,063,538	$ 1,039,651	$ 1,228,756	$ 1,198,673	$ 985,528	$ 872,938	$ 4,159,038	$ 4,285,895	$ 3,186,268
Income (loss) from operations	(282,645)	$ 135,960	$ (588,984)	$ 54,081	139,728	$ 76,256	$ 95,354	$ 102,238	(681,588)	413,576	323,984
Depreciation, depletion and amortization									525,508	466,587	365,066
Amortization of acquired sales contacts, net									(25,189)	(22,069)	35,606
Goodwill and other intangible asset impairment									346,423
Total assets	10,006,777				10,213,959				10,006,777	10,213,959	4,880,769
Capital expenditures									395,225	540,936	314,657
PRB [Member]
Segment Reporting Information [Line Items]
Coal Products and Services Revenue									1,524,537	1,646,947	1,606,236
Income (loss) from operations									100,679	180,730	146,555
Depreciation, depletion and amortization									166,539	171,693	185,218
Amortization of acquired sales contacts, net									(1,987)	19,458	35,606
Total assets	1,972,522				2,307,783				1,972,522	2,307,783	2,295,786
Capital expenditures									23,410	110,999	38,142
APP [Member]
Segment Reporting Information [Line Items]
Coal Products and Services Revenue									1,793,575	1,915,090	1,042,490
Income (loss) from operations									148,512	283,404	193,943
Depreciation, depletion and amortization									271,220	203,759	97,764
Amortization of acquired sales contacts, net									(23,925)	(39,988)	0
Total assets	3,875,105				4,740,723				3,875,105	4,740,723	706,624
Capital expenditures									275,476	217,435	70,839
WBIT [Member]
Segment Reporting Information [Line Items]
Coal Products and Services Revenue									728,089	672,766	537,542
Income (loss) from operations									144,421	119,665	58,082
Depreciation, depletion and amortization									71,696	81,235	80,497
Amortization of acquired sales contacts, net											0
Total assets	658,255				681,393				658,255	681,393	677,611
Capital expenditures									58,465	66,356	65,470
Other [Member]
Segment Reporting Information [Line Items]
Coal Products and Services Revenue									112,837	51,092	0
Income (loss) from operations									5,145	(4,685)	0
Depreciation, depletion and amortization									11,512	7,876	0
Amortization of acquired sales contacts, net									723	(1,539)	0
Total assets	176,032				581,040				176,032	581,040	0
Capital expenditures									9,928	28,243	0
Corporate, Other and Eliminations [Member]
Segment Reporting Information [Line Items]
Coal Products and Services Revenue											0
Income (loss) from operations									(1,080,345)	(165,538)	(74,596)
Depreciation, depletion and amortization									4,541	2,024	1,587
Amortization of acquired sales contacts, net											0
Total assets	$ 3,324,863				$ 1,903,020				3,324,863	1,903,020	1,200,748
Capital expenditures									$ 27,946	$ 117,903	$ 140,206

Segment Information (Reconciliation Statement Of Segment Income from Operations To Consolidated Income Before Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting [Abstract]
Income (loss) from operations	$ (282,645)	$ 135,960	$ (588,984)	$ 54,081	$ 139,728	$ 76,256	$ 95,354	$ 102,238	$ (681,588)	$ 413,576	$ 323,984
Interest expense									(317,626)	(230,186)	(142,549)
Interest income									5,478	3,309	2,449
Other nonoperating expenses									(23,668)	(51,448)	(6,776)
Income (loss) before income taxes									$ (1,017,404)	$ 135,251	$ 177,108

Quarterly Financial Information Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Coal Products and Services Revenue	$ 968,231	$ 1,087,618	$ 1,063,538	$ 1,039,651	$ 1,228,756	$ 1,198,673	$ 985,528	$ 872,938	$ 4,159,038	$ 4,285,895	$ 3,186,268
Gross Profit	37,176	69,249	54,984	63,704	154,388	120,085	172,234	130,523
Restructuring, Settlement and Impairment Provisions	0	(2,194)	525,762	0					523,568	7,316
Goodwill, Impairment Loss	230,632	0	115,791	0					(330,680)
Operating Income (Loss)	(282,645)	135,960	(588,984)	54,081	139,728	76,256	95,354	102,238	(681,588)	413,576	323,984
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ (295,423)	$ 45,751	$ (435,424)	$ 1,409	$ 71,215	$ 9,121	$ 6,630	$ 55,874	$ (683,687)	$ 142,840	$ 159,394
Earnings Per Share, Basic	$ (1.39)	$ 0.22	$ (2.05)	$ 0.01	$ 0.34	$ 0.04	$ 0.04	$ 0.34	$ (3.24)	$ 0.75	$ 0.98
Earnings Per Share, Diluted	$ (1.39)	$ 0.22	$ (2.05)	$ 0.01	$ 0.33	$ 0.04	$ 0.04	$ 0.34	$ (3.24)	$ 0.74	$ 0.97
Acquisition And Transition Costs										$ 47,360
ICG [Member]
Acquisition And Transition Costs		$ 4,700			$ 1,300		$ 98,200

Supplemental Condensed Consolidating Financial Information (Schedule Of Condensed Consolidating Statements Of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Condensed Financial Statement Line Items
Revenues	$ 968,231	$ 1,087,618	$ 1,063,538	$ 1,039,651	$ 1,228,756	$ 1,198,673	$ 985,528	$ 872,938	$ 4,159,038	$ 4,285,895	$ 3,186,268
Costs, expenses and other
Cost of sales									3,438,013	3,267,910	2,395,812
Depreciation, depletion and amortization									525,508	466,587	365,066
Amortization of acquired sales contracts, net									(25,189)	(22,069)	35,606
Change in fair value of coal derivatives and coal trading activities, net									(16,590)	(2,907)	8,924
Coal derivative settlements, non-hedging									(43,990)	7	(4,542)
Selling, general and administrative expenses									134,299	119,056	118,177
Contract settlement resulting from Patriot Coal bankruptcy									58,335
Legal contingencies									(79,532)
Mine closure and asset impairment costs	0	(2,194)	525,762	0					523,568	7,316
Goodwill and other intangible asset impairment									346,423
Acquisition And Transition Costs										47,360
Gain on Knight Hawk transaction											(41,577)
Other operating (income) expense, net									(20,219)	(10,941)	(15,182)
Total operating expenses									4,840,626	3,872,319	2,862,284
Income from investment in subsidiaries
Income (loss) from operations	(282,645)	135,960	(588,984)	54,081	139,728	76,256	95,354	102,238	(681,588)	413,576	323,984
Interest expense, net:
Interest expense									(317,626)	(230,186)	(142,549)
Interest income									5,478	3,309	2,449
Interest expense, net									(312,148)	(226,877)	(140,100)
Other non-operating expense
Net loss resulting from early retirement and refinancing of debt									(23,668)	(1,958)	(6,776)
Bridge financing costs related to ICG										(49,490)
Other nonoperating expense, Total									(23,668)	(51,448)	(6,776)
Income (loss) before income taxes									(1,017,404)	135,251	177,108
Provision for (benefit from) income taxes									(333,717)	(7,589)	17,714
Net income (loss)	$ (295,423)	$ 45,751	$ (435,424)	$ 1,409	$ 71,215	$ 9,121	$ 6,630	$ 55,874	(683,687)	142,840	159,394
Less: Net income attributable to noncontrolling interest									(268)	(1,157)	(537)
Net income (loss) attributable to Arch Coal, Inc.									(683,955)	141,683	158,857
Total comprehensive income (loss)									(692,239)	141,240	172,885
Parent/Issuer [Member]
Condensed Financial Statement Line Items
Revenues
Costs, expenses and other
Cost of sales									10,918	22,926	11,523
Depreciation, depletion and amortization									5,392	2,876	2,933
Amortization of acquired sales contracts, net
Change in fair value of coal derivatives and coal trading activities, net
Coal derivative settlements, non-hedging
Selling, general and administrative expenses									84,198	74,589	79,580
Contract settlement resulting from Patriot Coal bankruptcy
Legal contingencies
Mine closure and asset impairment costs										7,316
Goodwill and other intangible asset impairment
Acquisition And Transition Costs										47,360
Gain on Knight Hawk transaction
Other operating (income) expense, net									(13,391)	(23,306)	(10,258)
Total operating expenses									87,117	131,761	83,778
Income from investment in subsidiaries									(569,795)	556,442	393,363
Income (loss) from operations									(656,912)	424,681	309,585
Interest expense, net:
Interest expense									(366,614)	(256,221)	(143,606)
Interest income									28,097	16,281	11,129
Interest expense, net									(338,517)	(239,940)	(132,477)
Other non-operating expense
Net loss resulting from early retirement and refinancing of debt									(21,975)
Bridge financing costs related to ICG										(49,490)
Other nonoperating expense, Total									(21,975)	(49,490)
Income (loss) before income taxes									(1,017,404)	135,251	177,108
Provision for (benefit from) income taxes									(333,717)	(7,589)	17,714
Net income (loss)									(683,687)	142,840	159,394
Less: Net income attributable to noncontrolling interest									(268)	(1,157)	(537)
Net income (loss) attributable to Arch Coal, Inc.									(683,955)	141,683	158,857
Total comprehensive income (loss)										141,240	172,885
Guarantor Subsidiaries [Member]
Condensed Financial Statement Line Items
Revenues									4,159,038	4,285,895	3,186,268
Costs, expenses and other
Cost of sales									3,427,095	3,244,984	2,384,289
Depreciation, depletion and amortization									520,083	463,711	362,133
Amortization of acquired sales contracts, net									(25,189)	(22,069)	35,606
Change in fair value of coal derivatives and coal trading activities, net									(16,590)	(2,907)	8,924
Coal derivative settlements, non-hedging									(43,990)	7	(4,542)
Selling, general and administrative expenses									41,316	40,940	36,091
Contract settlement resulting from Patriot Coal bankruptcy									58,335
Legal contingencies									(79,532)
Mine closure and asset impairment costs									523,568
Goodwill and other intangible asset impairment									346,423
Acquisition And Transition Costs
Gain on Knight Hawk transaction											(41,577)
Other operating (income) expense, net									9,559	12,615	(4,924)
Total operating expenses									4,761,078	3,737,281	2,776,000
Income from investment in subsidiaries
Income (loss) from operations									(602,040)	548,614	410,268
Interest expense, net:
Interest expense									(35,207)	(46,565)	(64,377)
Interest income									57,303	55,072	52,899
Interest expense, net									22,096	8,507	(11,478)
Other non-operating expense
Net loss resulting from early retirement and refinancing of debt									(1,693)	(1,958)	(6,776)
Bridge financing costs related to ICG
Other nonoperating expense, Total									(1,693)	(1,958)	(6,776)
Income (loss) before income taxes									(581,637)	555,163	392,014
Provision for (benefit from) income taxes
Net income (loss)									(581,637)	555,163	392,014
Less: Net income attributable to noncontrolling interest
Net income (loss) attributable to Arch Coal, Inc.									(581,637)	555,163	392,014
Total comprehensive income (loss)										552,663	400,664
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statement Line Items
Revenues
Costs, expenses and other
Cost of sales
Depreciation, depletion and amortization									33
Amortization of acquired sales contracts, net
Change in fair value of coal derivatives and coal trading activities, net
Coal derivative settlements, non-hedging
Selling, general and administrative expenses									8,785	3,527	2,506
Contract settlement resulting from Patriot Coal bankruptcy
Legal contingencies
Mine closure and asset impairment costs
Goodwill and other intangible asset impairment
Acquisition And Transition Costs
Gain on Knight Hawk transaction
Other operating (income) expense, net									(16,387)	(250)
Total operating expenses									(7,569)	3,277	2,506
Income from investment in subsidiaries
Income (loss) from operations									7,569	(3,277)	(2,506)
Interest expense, net:
Interest expense									(3,221)	(2,224)	(2,849)
Interest income									7,494	6,780	6,704
Interest expense, net									4,273	4,556	3,855
Other non-operating expense
Net loss resulting from early retirement and refinancing of debt
Bridge financing costs related to ICG
Other nonoperating expense, Total
Income (loss) before income taxes									11,842	1,279	1,349
Provision for (benefit from) income taxes
Net income (loss)									11,842	1,279	1,349
Less: Net income attributable to noncontrolling interest
Net income (loss) attributable to Arch Coal, Inc.									11,842	1,279	1,349
Total comprehensive income (loss)										1,279	1,349
Eliminations [Member]
Condensed Financial Statement Line Items
Revenues
Costs, expenses and other
Cost of sales
Depreciation, depletion and amortization
Amortization of acquired sales contracts, net
Change in fair value of coal derivatives and coal trading activities, net
Coal derivative settlements, non-hedging
Selling, general and administrative expenses
Contract settlement resulting from Patriot Coal bankruptcy
Legal contingencies
Mine closure and asset impairment costs
Goodwill and other intangible asset impairment
Acquisition And Transition Costs
Gain on Knight Hawk transaction
Other operating (income) expense, net
Total operating expenses
Income from investment in subsidiaries									569,795	(556,442)	(393,363)
Income (loss) from operations									569,795	(556,442)	(393,363)
Interest expense, net:
Interest expense									87,416	74,824	68,283
Interest income									(87,416)	(74,824)	(68,283)
Interest expense, net
Other non-operating expense
Net loss resulting from early retirement and refinancing of debt
Bridge financing costs related to ICG
Other nonoperating expense, Total
Income (loss) before income taxes									569,795	(556,442)	(393,363)
Provision for (benefit from) income taxes
Net income (loss)									569,795	(556,442)	(393,363)
Less: Net income attributable to noncontrolling interest
Net income (loss) attributable to Arch Coal, Inc.									$ 569,795	(556,442)	(393,363)
Total comprehensive income (loss)										$ (553,942)	$ (402,013)

Supplemental Condensed Consolidating Financial Information (Schedule Of Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Assets
Cash and cash equivalents	$ 784,622	$ 138,149	$ 93,593	$ 61,138
Restricted cash	3,453	10,322
Short term investments	234,305
Receivables	332,080	469,179
Inventories	365,424	377,490
Other	194,220	187,634
Total current assets	1,914,104	1,182,774
Property, plant and equipment, net	7,337,098	7,949,150
Investment in subsidiaries
Intercompany receivables
Note receivable from Arch Western
Other	755,575	1,082,035
Assets, Noncurrent	755,575	1,082,035
Total assets	10,006,777	10,213,959	4,880,769
Liabilities and Stockholders’ Equity
Accounts payable	224,418	383,782
Accrued expenses and other current liabilities	319,755	356,035
Current maturities of debt and short-term borrowings	32,896	280,851
Total current liabilities	577,069	1,020,668
Long-term debt	5,085,879	3,762,297
Note payable to Arch Coal
Asset retirement obligations	409,705	446,784
Accrued pension benefits	67,630	48,244
Accrued postretirement benefits other than pension	45,086	42,309
Accrued workers' compensation	81,629	71,948
Deferred income taxes	664,182	976,753
Other noncurrent liabilities	221,030	255,382
Total liabilities	7,152,210	6,624,385
Redeemable noncontrolling interest		11,534
Stockholders' equity	2,854,567	3,578,040	2,237,507	2,115,106
Total liabilities and stockholders' equity	10,006,777	10,213,959
Parent/Issuer [Member]
Assets
Cash and cash equivalents	671,313	61,375	13,713	54,255
Restricted cash	3,453	10,322
Short term investments	234,305
Receivables	49,281	65,187
Inventories
Other	106,786	81,732
Total current assets	1,065,138	218,616
Property, plant and equipment, net	27,476	21,241
Investment in subsidiaries	8,254,508	8,813,080
Intercompany receivables	(1,367,739)	(1,190,342)
Note receivable from Arch Western	675,000	225,000
Other	187,171	(85,668)
Assets, Noncurrent	7,748,940	7,762,070
Total assets	8,841,554	8,001,927
Liabilities and Stockholders’ Equity
Accounts payable	19,859	30,576
Accrued expenses and other current liabilities	65,293	75,121
Current maturities of debt and short-term borrowings	32,054	172,564
Total current liabilities	117,206	278,261
Long-term debt	5,061,925	3,308,674
Note payable to Arch Coal
Asset retirement obligations	1,646	877
Accrued pension benefits	33,456	19,198
Accrued postretirement benefits other than pension	13,953	13,843
Accrued workers' compensation	25,323	17,272
Deferred income taxes	664,182	621,483
Other noncurrent liabilities	69,296	152,745
Total liabilities	5,986,987	4,412,353
Redeemable noncontrolling interest		11,534
Stockholders' equity	2,854,567	3,578,040
Total liabilities and stockholders' equity	8,841,554	8,001,927
Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents	100,468	75,425	79,880	6,883
Restricted cash
Short term investments
Receivables	40,452	27,001
Inventories	365,424	377,490
Other	86,877	105,282
Total current assets	593,221	585,198
Property, plant and equipment, net	7,309,550	7,918,816
Investment in subsidiaries
Intercompany receivables	1,600,311	1,448,902
Note receivable from Arch Western
Other	568,314	1,167,501
Assets, Noncurrent	2,168,625	2,616,403
Total assets	10,071,396	11,120,417
Liabilities and Stockholders’ Equity
Accounts payable	204,370	353,180
Accrued expenses and other current liabilities	259,162	282,446
Current maturities of debt and short-term borrowings	842	1,987
Total current liabilities	464,374	637,613
Long-term debt	23,954	453,623
Note payable to Arch Coal	675,000	225,000
Asset retirement obligations	408,059	445,907
Accrued pension benefits	34,174	29,046
Accrued postretirement benefits other than pension	31,133	28,466
Accrued workers' compensation	56,306	54,676
Deferred income taxes		355,270
Other noncurrent liabilities	151,360	102,553
Total liabilities	1,844,360	2,332,154
Redeemable noncontrolling interest
Stockholders' equity	8,227,036	8,788,263
Total liabilities and stockholders' equity	10,071,396	11,120,417
Non-Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents	12,841	1,349
Restricted cash
Short term investments
Receivables	247,171	378,608
Inventories
Other	557	620
Total current assets	260,569	380,577
Property, plant and equipment, net	72	9,093
Investment in subsidiaries
Intercompany receivables	(232,572)	(258,560)
Note receivable from Arch Western
Other	90	202
Assets, Noncurrent	(232,482)	(258,358)
Total assets	28,159	131,312
Liabilities and Stockholders’ Equity
Accounts payable	189	26
Accrued expenses and other current liabilities	124	85
Current maturities of debt and short-term borrowings		106,300
Total current liabilities	313	106,411
Long-term debt
Note payable to Arch Coal
Asset retirement obligations
Accrued pension benefits
Accrued postretirement benefits other than pension
Accrued workers' compensation
Deferred income taxes
Other noncurrent liabilities	374	84
Total liabilities	687	106,495
Redeemable noncontrolling interest
Stockholders' equity	27,472	24,817
Total liabilities and stockholders' equity	28,159	131,312
Eliminations [Member]
Assets
Cash and cash equivalents
Restricted cash
Short term investments
Receivables	(4,824)	(1,617)
Inventories
Other
Total current assets	(4,824)	(1,617)
Property, plant and equipment, net
Investment in subsidiaries	(8,254,508)	(8,813,080)
Intercompany receivables
Note receivable from Arch Western	(675,000)	(225,000)
Other
Assets, Noncurrent	(8,929,508)	(9,038,080)
Total assets	(8,934,332)	(9,039,697)
Liabilities and Stockholders’ Equity
Accounts payable
Accrued expenses and other current liabilities	(4,824)	(1,617)
Current maturities of debt and short-term borrowings
Total current liabilities	(4,824)	(1,617)
Long-term debt
Note payable to Arch Coal	(675,000)	(225,000)
Asset retirement obligations
Accrued pension benefits
Accrued postretirement benefits other than pension
Accrued workers' compensation
Deferred income taxes
Other noncurrent liabilities
Total liabilities	(679,824)	(226,617)
Redeemable noncontrolling interest
Stockholders' equity	(8,254,508)	(8,813,080)
Total liabilities and stockholders' equity	$ (8,934,332)	$ (9,039,697)

Supplemental Condensed Consolidating Financial Information (Schedule Of Condensed Consolidating Statements Of Cash Flows) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash provided by (used in) operating activities	$ 332,804	$ 642,242	$ 697,147
Investing Activities
Acquisition of ICG, net of cash acquired		(2,894,339)
Change in restricted cash	6,869	5,167
Capital expenditures	(395,225)	(540,936)	(314,657)
Proceeds from dispositions of property, plant and equipment	22,825	25,887	330
Investments in and advances to affiliates	(17,758)	(61,909)	(46,185)
Purchases of short term investments	(236,862)
Proceeds from Sale of Short-term Investments	1,754
Purchase of noncontrolling interest	(17,500)
Additions to prepaid royalties	(13,269)	(29,957)	(27,355)
Consideration paid related to prior business acquisition		(829)	(1,262)
Cash used in investing activities	(649,166)	(3,496,916)	(389,129)
Financing Activities
Contributions from parent
Proceeds from the issuance of senior notes	359,753	2,000,000	500,000
Proceeds from the sale of common stock, net		1,267,933
Proceeds from term note	1,633,500
Payments to retire debt	(452,934)	(605,178)	(505,627)
Net increase (decrease) in borrowings under lines of credit and commercial paper program	(481,300)	424,396	(196,549)
Payments on term note	(7,625)
Net payments on other debt	(682)	5,334	82
Debt financing costs	(50,568)	(114,823)	(12,751)
Dividends paid	(42,440)	(80,748)	(63,373)
Issuance of common stock under incentive plans	5,131	2,316	1,764
Proceeds from Noncontrolling Interests			891
Transactions with affiliates, net
Cash provided by (used in) financing activities	962,835	2,899,230	(275,563)
Increase (decrease) in cash and cash equivalents	646,473	44,556	32,455
Cash and cash equivalents, beginning of period	138,149	93,593	61,138
Cash and cash equivalents, end of period	784,622	138,149	93,593
Parent/Issuer [Member]
Cash provided by (used in) operating activities	(571,576)	(187,039)	(230,966)
Investing Activities
Acquisition of ICG, net of cash acquired		(2,894,339)
Change in restricted cash	6,869	5,167
Capital expenditures	(4,424)	(12,809)	(4,814)
Proceeds from dispositions of property, plant and equipment
Investments in and advances to affiliates	(6,287)	(633,534)	(13,821)
Purchases of short term investments	(236,862)
Proceeds from Sale of Short-term Investments	1,754
Purchase of noncontrolling interest	(17,500)
Additions to prepaid royalties
Consideration paid related to prior business acquisition		(829)	(1,262)
Cash used in investing activities	(256,450)	(3,536,344)	(19,897)
Financing Activities
Contributions from parent
Proceeds from the issuance of senior notes	359,753	2,000,000	500,000
Proceeds from the sale of common stock, net		1,267,933
Proceeds from term note	1,633,500
Payments to retire debt
Net increase (decrease) in borrowings under lines of credit and commercial paper program	(375,000)	375,000	(120,000)
Payments on term note	(7,625)
Net payments on other debt	(682)	5,334	82
Debt financing costs	(50,022)	(114,799)	(12,022)
Dividends paid	(42,440)	(80,748)	(63,373)
Issuance of common stock under incentive plans	5,131	2,316	1,764
Proceeds from Noncontrolling Interests			891
Transactions with affiliates, net	(84,651)	316,009	(97,021)
Cash provided by (used in) financing activities	1,437,964	3,771,045	210,321
Increase (decrease) in cash and cash equivalents	609,938	47,662	(40,542)
Cash and cash equivalents, beginning of period	61,375	13,713	54,255
Cash and cash equivalents, end of period	671,313	61,375	13,713
Guarantor Subsidiaries [Member]
Cash provided by (used in) operating activities	781,551	998,082	943,361
Investing Activities
Acquisition of ICG, net of cash acquired
Change in restricted cash
Capital expenditures	(390,801)	(528,021)	(309,843)
Proceeds from dispositions of property, plant and equipment	1,328	25,887	330
Investments in and advances to affiliates	(13,134)	(33,553)	(32,364)
Purchases of short term investments
Proceeds from Sale of Short-term Investments
Purchase of noncontrolling interest
Additions to prepaid royalties	(13,269)	(29,957)	(27,355)
Consideration paid related to prior business acquisition
Cash used in investing activities	(415,876)	(565,644)	(369,232)
Financing Activities
Contributions from parent	1,663	605,178
Proceeds from the issuance of senior notes
Proceeds from the sale of common stock, net
Proceeds from term note
Payments to retire debt	(452,934)	(605,178)	(505,627)
Net increase (decrease) in borrowings under lines of credit and commercial paper program		(56,904)	7,451
Payments on term note
Net payments on other debt
Debt financing costs		(16)	(390)
Dividends paid
Issuance of common stock under incentive plans
Proceeds from Noncontrolling Interests
Transactions with affiliates, net	110,639	(379,973)	(2,566)
Cash provided by (used in) financing activities	(340,632)	(436,893)	(501,132)
Increase (decrease) in cash and cash equivalents	25,043	(4,455)	72,997
Cash and cash equivalents, beginning of period	75,425	79,880	6,883
Cash and cash equivalents, end of period	100,468	75,425	79,880
Non-Guarantor Subsidiaries [Member]
Cash provided by (used in) operating activities	122,829	(168,801)	(15,248)
Investing Activities
Acquisition of ICG, net of cash acquired
Change in restricted cash
Capital expenditures		(106)
Proceeds from dispositions of property, plant and equipment	21,497
Investments in and advances to affiliates
Purchases of short term investments
Proceeds from Sale of Short-term Investments
Purchase of noncontrolling interest
Additions to prepaid royalties
Consideration paid related to prior business acquisition
Cash used in investing activities	21,497	(106)
Financing Activities
Contributions from parent
Proceeds from the issuance of senior notes
Proceeds from the sale of common stock, net
Proceeds from term note
Payments to retire debt
Net increase (decrease) in borrowings under lines of credit and commercial paper program	(106,300)	106,300	(84,000)
Payments on term note
Net payments on other debt
Debt financing costs	(546)	(8)	(339)
Dividends paid
Issuance of common stock under incentive plans
Proceeds from Noncontrolling Interests
Transactions with affiliates, net	(25,988)	63,964	99,587
Cash provided by (used in) financing activities	(132,834)	170,256	15,248
Increase (decrease) in cash and cash equivalents	11,492	1,349
Cash and cash equivalents, beginning of period	1,349
Cash and cash equivalents, end of period	12,841	1,349
Eliminations [Member]
Cash provided by (used in) operating activities
Investing Activities
Acquisition of ICG, net of cash acquired
Change in restricted cash
Capital expenditures
Proceeds from dispositions of property, plant and equipment
Investments in and advances to affiliates	1,663	605,178
Purchases of short term investments
Proceeds from Sale of Short-term Investments
Purchase of noncontrolling interest
Additions to prepaid royalties
Consideration paid related to prior business acquisition
Cash used in investing activities	1,663	605,178
Financing Activities
Contributions from parent	(1,663)	(605,178)
Proceeds from the issuance of senior notes
Proceeds from the sale of common stock, net
Proceeds from term note
Payments to retire debt
Net increase (decrease) in borrowings under lines of credit and commercial paper program
Payments on term note
Net payments on other debt
Debt financing costs
Dividends paid
Issuance of common stock under incentive plans
Proceeds from Noncontrolling Interests
Transactions with affiliates, net
Cash provided by (used in) financing activities	(1,663)	(605,178)
Increase (decrease) in cash and cash equivalents
Cash and cash equivalents, beginning of period
Cash and cash equivalents, end of period

Label	Element	Value
ShareBasedCompensationArrangementByShareBasedPaymentAwardUnvestedOptionsOutstandingNumber	aci_Sharebasedcompensationarrangementbysharebasedpaymentawardunvestedoptionsoutstandingnumber	2,369,000
ShareBasedCompensationArrangementByShareBasedPaymentAwardUnvestedOptionsWeightedAverageGrantDateFairValue	aci_Sharebasedcompensationarrangementbysharebasedpaymentawardunvestedoptionsweightedaveragegrantdatefairvalue	7.77

Employee Benefit Plans Employee Benefit Plans (Schedule of Allocation of Plan Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 322,874	$ 285,074
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	97,835	92,210
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	225,039	192,864
U.S. Small-Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	13,099	11,178
U.S. Small-Cap [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	13,099	11,178
U.S. Small-Cap [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets
U.S. Mid-Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	43,946	50,264
U.S. Mid-Cap [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	12,717	23,474
U.S. Mid-Cap [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	31,229	26,790
U.S. Large-Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	102,922	91,561
U.S. Large-Cap [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	48,536	44,820
U.S. Large-Cap [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	54,386	46,741
Non-U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	27,251	22,509
Non-U.S. [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets
Non-U.S. [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	27,251	22,509
U.S. Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	24,202	13,454
U.S. Government Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	23,483	12,738
U.S. Government Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	719	716
Non-U.S. Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	3,681	2,968
Non-U.S. Government Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets
Non-U.S. Government Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	3,681	2,968
U.S. governement asset and mortgage backed securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	781	800
U.S. governement asset and mortgage backed securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets
U.S. governement asset and mortgage backed securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	781	800
Corporate fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	14,016	14,004
Corporate fixed income [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets
Corporate fixed income [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	14,016	14,004
State and Local Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	9,903	18,416
State and Local Government Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets
State and Local Government Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	9,903	18,416
Other fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	61,765	51,470
Other fixed income [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets
Other fixed income [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	61,765	51,470
Short-term Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	20,894	8,029
Short-term Investments [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets
Short-term Investments [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	20,894	8,029
Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	414	421
Other Investments [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets
Other Investments [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 414	$ 421