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Document And Entity Information - shares	9 Months Ended
Document And Entity Information - shares	Sep. 30, 2013	Nov. 04, 2013
Document and Entity Information [Abstract]
Entity Registrant Name	ARCH COAL INC
Entity Central Index Key	0001037676
Document Type	10-Q
Document Period End Date	Sep. 30, 2013
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q3
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		212,279,999

Consolidated Statements Of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Statement [Abstract]
Revenues	$ 791,269	$ 975,170	$ 2,294,971	$ 2,901,092
Costs and Expenses [Abstract]
Cost of sales (exclusive of items shown separately below)	688,712	808,489	1,994,653	2,414,306
Depreciation, depletion and amortization	106,323	118,942	327,601	374,631
Amortization of acquired sales contracts, net	(2,568)	(4,093)	(7,587)	(22,561)
Change in fair value of coal derivatives and coal trading activities, net	9,753	5,840	2,053	(29,827)
Asset impairment and mine closure costs	200,397	(2,144)	220,879	523,439
Goodwill impairment				115,791
Legal contingencies		(79,532)		(79,532)
Selling, general and administrative expenses	28,800	33,266	96,311	99,305
Other operating income, net	(5,395)	(24,840)	(16,476)	(44,606)
Total operating expenses	1,026,022	855,928	2,617,434	3,350,946
Income (loss) from operations	(234,753)	119,242	(322,463)	(449,854)
Interest expense, net
Interest expense	(95,624)	(75,710)	(285,454)	(229,210)
Interest and investment income	697	1,459	4,749	3,568
Interest expense, net	(94,927)	(74,251)	(280,705)	(225,642)
Other nonoperating expense:
Net loss resulting from early retirement and refinancing of debt				(19,042)
Loss from continuing operations before income taxes	(329,680)	44,991	(603,168)	(694,538)
Provision for (benefit from) income taxes	(121,913)	20,318	(230,734)	(262,656)
Income (loss) from continuing operations	(207,767)	24,673	(372,434)	(431,882)
Income from discontinued operations, including gain on sale - net of tax	79,404	21,078	101,816	43,618
Net income (loss)	(128,363)	45,751	(270,618)	(388,264)
Less: Net income attributable to noncontrolling interest				(268)
Net income (loss) attributable to Arch Coal, Inc.	$ (128,363)	$ 45,751	$ (270,618)	$ (388,532)
Earnings (loss) per common share
Income (Loss) from Continuing Operations, Per Basic Share	$ (0.98)	$ 0.12	$ (1.76)	$ (2.04)
Income (Loss) from Continuing Operations, Per Diluted Share	(0.98)	0.12	(1.76)	(2.04)
Basic earnings (loss) per common share	(0.61)	0.22	(1.28)	(1.83)
Diluted earnings (loss) per common share	$ (0.61)	$ 0.22	$ (1.28)	$ (1.83)
Weighted average shares outstanding
Basic, weighted average shares outstanding	212,111	212,053	212,085	211,931
Diluted, weighted average shares outstanding	212,111	212,076	212,085	211,931
Dividends declared per common share	$ 0.03	$ 0.03	$ 0.09	$ 0.17

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net income (loss)	$ (128,363)	$ 45,751	$ (270,618)	$ (388,264)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax	1,346	(439)	(224)	10,586
Derivatives Qualifying as Hedges, Tax benefit	(486)	157	82	(3,810)
Derivatives Qualifying as Hedges, Adjustment, Net of Tax	860	(282)	(142)	6,776
Pension and Other Postretirement Benefit Plans, Total comprehensive income (loss) before tax	1,277	(989)	4,981	(5,957)
Pension and Other Postretirement Benefit Plans, Tax impact	(458)	374	(1,791)	2,162
Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	819	(615)	3,190	(3,795)
Available-for-sale Securities Adjustment, Total comprehensive income (loss) before tax	1,136	(869)	7,648	(377)
Available-for-sale Securities, Tax benefit	(448)	314	(2,795)	137
Available-for-sale Securities Adjustment, Net of Tax	688	(555)	4,853	(240)
Total other comprehensive income (loss)	2,367	(1,452)	7,901	2,741
Total comprehensive income (loss)	$ (125,996)	$ 44,299	$ (262,717)	$ (385,523)

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2013	Dec. 31, 2012
Current assets
Cash and cash equivalents	$ 1,133,128	$ 784,622
Restricted cash		3,453
Short term investments	248,724	234,305
Trade accounts receivable	190,723	247,539
Other receivables	24,116	84,541
Inventories	287,409	365,424
Prepaid royalties	8,350	11,416
Deferred income taxes	67,381	67,360
Coal derivative assets	22,836	22,975
Other current assets	46,972	92,469
Total current assets	2,029,639	1,914,104
Property, plant and equipment, net	6,778,225	7,337,098
Other assets
Prepaid royalties	85,001	87,773
Goodwill	265,423	265,423
Equity investments	223,554	242,215
Other noncurrent assets	149,613	160,164
Total other assets	723,591	755,575
Total assets	9,531,455	10,006,777
Current liabilities
Accounts payable	207,273	224,418
Coal derivative liabilities	421	1,737
Accrued expenses and other current liabilities	349,033	318,018
Current maturities of debt	23,050	32,896
Total current liabilities	579,777	577,069
Long-term debt	5,074,384	5,085,879
Asset retirement obligations	411,121	409,705
Accrued pension benefits	68,539	67,630
Accrued postretirement benefits other than pension	44,279	45,086
Accrued workers’ compensation	82,014	81,629
Deferred income taxes	484,130	664,182
Other noncurrent liabilities	205,557	221,030
Total liabilities	6,949,801	7,152,210
Stockholders' equity
Common stock, $0.01 par value, authorized 260,000 shares, issued 213,792 and 213,759 shares at September 30, 2013 and December 31, 2012	2,141	2,141
Paid-in capital	3,035,732	3,026,823
Treasury stock, at cost	(53,848)	(53,848)
Accumulated deficit	(393,765)	(104,042)
Accumulated other comprehensive loss	(8,606)	(16,507)
Total stockholders’ equity	2,581,654	2,854,567
Total liabilities and stockholders’ equity	$ 9,531,455	$ 10,006,777

Balance Sheet Parenthetical (Parentheticals) - $ / shares	Sep. 30, 2013	Dec. 31, 2012
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	260,000,000	260,000,000
Common stock, shares issued	213,792,000	213,759,000

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Operating activties
Net income (loss)	$ (270,618)	$ (388,264)
Adjustments to reconcile net loss to cash provided by operating activities:
Depreciation, depletion and amortization	348,863	399,672
Amortization of acquired sales contracts, net	(7,587)	(22,561)
Amortization relating to financing activities	18,525	14,345
Prepaid royalties expensed	11,973	19,802
Employee stock-based compensation expense	8,909	9,435
Asset impairment and noncash mine closure costs	220,879	501,942
Amortization of premiums on debt securities held	3,679
Gain on sale of Canyon Fuel	(115,679)
Goodwill impairment		115,791
Net loss resulting from early retirement of debt and financing activities		19,042
Changes in:
Receivables	72,436	102,252
Inventories	21,387	(16,635)
Coal derivative assets and liabilities	(1,568)	(29,523)
Accounts payable, accrued expenses and other current liabilities	19,287	(51,968)
Income taxes, net	787	22,048
Deferred income taxes	184,418	255,530
Other	39,737	(83,453)
Cash provided by operating activities	186,592	356,395
Investing activities
Capital expenditures	(223,168)	(303,968)
Minimum royalty payments	(10,901)	(9,192)
Proceeds from dispositions of property, plant and equipment	8,799	22,624
Proceeds from sale-leaseback transactions	34,919
Proceeds from sale of Canyon Fuel	422,663
Purchases of short term investments	(85,418)	(99,628)
Proceeds from sales of short term investments	67,255
Investments in and advances to affiliates	(11,124)	(12,685)
Purchase of noncontrolling interest		(17,500)
Change in restricted cash	3,453	6,872
Cash provided by (used in) investing activities	206,478	(413,477)
Financing activities
Proceeds from issuance of term loan		1,386,000
Payments on term loan	(12,375)	(3,500)
Payments to retire debt	(384)	(452,806)
Net decrease in borrowings under lines of credit		(381,300)
Net payments on other debt	(12,700)	(13,078)
Debt financing costs		(34,686)
Dividends paid	(19,105)	(36,072)
Proceeds from exercise of options under incentive plans		5,131
Cash provided by (used in) financing activities	(44,564)	469,689
Increase in cash and cash equivalents	348,506	412,607
Cash and cash equivalents, beginning of period	784,622	138,149
Cash and cash equivalents, end of period	$ 1,133,128	$ 550,756

Basis of Presentation	9 Months Ended
Basis of Presentation	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	Basis of Presentation The accompanying unaudited condensed 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 steel producers both in the United States and around the world. The Company currently operates mining complexes in West Virginia, Kentucky, Maryland, Virginia, Illinois, Wyoming and Colorado. In addition, the Company is developing a metallurgical coal mine in West Virginia. All subsidiaries are wholly-owned. Intercompany transactions and accounts have been eliminated in consolidation. The Company completed the sale of a subsidiary comprised of three mining complexes in the Western Bituminous reportable segment ("WBIT") on August 16, 2013. The results of these mining complexes have been segregated from continuing operations and are reflected, net of tax, as discontinued operations in the condensed consolidated statements of operations for all periods presented. See further discussion in Note 3, "Discontinued Operations". In response to decreasing demand for thermal coal in Appalachia, the Company closed four mining complexes, temporarily idled a fifth complex, and curtailed production at other mines in the region in the second quarter of 2012. The operations continued to ship from inventory into the third quarter of 2012. The results for the closed and idled complexes are reflected in continuing operations in the condensed consolidating statements of operations for the three and nine month periods ended September 30, 2012. See further discussion in Note 5, "Impairment Charges". The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States for interim financial reporting and U.S. Securities and Exchange Commission regulations. In the opinion of management, all adjustments, consisting of normal, recurring accruals considered necessary for a fair presentation, have been included. Results of operations for the three and nine month periods ended September 30, 2013 are not necessarily indicative of results to be expected for the year ending December 31, 2013. These financial statements should be read in conjunction with the audited financial statements and related notes as of and for the year ended December 31, 2012 included in the Company’s Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission.

- Definition

The entire disclosure for organization, consolidation and basis of presentation of financial statements disclosure.

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+ Details

Accounting Policies Accounting Policies	9 Months Ended
Accounting Policies Accounting Policies	Sep. 30, 2013
Accounting Policies [Abstract]
Accounting Policies	Accounting Policies There is no new accounting guidance that is expected to have a significant impact on the Company’s financial statements.

Discontinued Operations

9 Months Ended

Sep. 30, 2013

Discontinued Operations and Disposal Groups [Abstract]

Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]

Discontinued Operations

As part of a strategy to divest its non-core thermal coal assets, the Company entered into a definitive agreement on June 27, 2013 to sell Canyon Fuel Company, LLC (Canyon Fuel), to Bowie Resources, LLC. Canyon Fuel operated two longwall mining complexes and a continuous miner operation in Utah. The sale was completed on August 16, 2013, for $422.7 million in cash, including adjustments to initial working capital estimates. The purchase price is subject to final working capital adjustments, which we do not expect to have a significant impact on our results of operations or liquidity.

The following table summarizes the results of discontinued operations:



	Three Months Ended September 30,					Nine Months Ended September 30,
	2013		2012			2013		2012
	(In thousands)
Total Revenues	$	45,763	$	112,448		$	219,002	$	289,715
Income from discontinued operations before income taxes	$	3,429	$	16,718		$	32,166	$	50,911
Gain on sale	115,679		—			115,679		—
Income tax expense (benefit)	39,704		(4,360		)	46,029		7,293
Income from discontinued operations, including gain on sale - net of tax	$	79,404	$	21,078		$	101,816	$	43,618
Basic earnings per common share from discontinued operations	$	0.37	$	0.10		$	0.48	$	0.21
Diluted earnings per common share from discontinued operations	$	0.37	$	0.10		$	0.48	$	0.21

- Definition

The entire disclosure for the facts and circumstances leading to the completed or expected disposal, manner and timing of disposal, the gain (loss) recognized in the income statement and the income statement caption that includes that gain (loss), amounts of revenues and pretax profit or loss reported in discontinued operations, the segment in which the disposal group was reported, and the classification (whether sold or classified as held for sale) and carrying value of the assets and liabilities comprising the disposal group. Includes all disposal groups, including those classified as components of the entity (discontinued operations).

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+ Details

Accumulated Other Comprehensive Income (Loss)

9 Months Ended

Sep. 30, 2013

Accumulated Other Comprehensive Income (Loss) [Abstract]

Comprehensive Income (Loss) Note [Text Block]

Accumulated Other Comprehensive Loss

Other comprehensive loss includes transactions recorded in stockholders' equity during the year, excluding net income and transactions with stockholders. In February 2013, the FASB issued ASU 2013-02, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income. The standard requires that companies present, either parenthetically on the face of the financial statements or in a single note, the effect of significant amounts reclassified from each component of accumulated other comprehensive income and the income statement line items affected by the reclassification. The Company adopted the provisions of the new guidance in the first quarter of 2013.

The following items are included in accumulated other comprehensive loss:



				Pension,
				Postretirement
				and Other						Accumulated
				Post-						Other
	Derivative			Employment			Available-for-			Comprehensive
	Instruments			Benefits			Sale Securities			Loss
	(In thousands)
Balance at December 31, 2012	$	2,244		$	(18,286	)	$	(465	)	$	(16,507	)
Unrealized gains	1,197			1,938			4,653			7,788
Amounts reclassified from accumulated other comprehensive income	(1,339		)	1,252			200			113
Balance at September 30, 2013	$	2,102		$	(15,096	)	$	4,388		$	(8,606	)

The following amounts were reclassified out of accumulated other comprehensive loss:



	Amount Reclassified from
	Accumulated Comprehensive Loss							Line Item in the
Details about accumulated other	Three Months Ended			Nine Months Ended				Condensed Consolidated
comprehensive income components	September 30, 2013			September 30, 2013				Statement of Operations
	(In thousands)
Derivative instruments	$	692		$	2,093			Revenues
	(249		)	(754		)		Provision for (benefit from) income taxes
	$	443		$	1,339			Net of tax

Pension, postretirement and other post-employment benefits
Amortization of prior service credits	$	5,573		$	11,154		¹
Amortization of actuarial gains (losses), net	(3,823		)	(13,108		)	¹
	1,750			(1,954		)		Total before tax
	(631		)	702				Provision for (benefit from) income taxes
	$	1,119		$	(1,252	)		Net of tax

Available-for-sale securities	$	(4	)	$	(313	)	²	Interest and investment income
	2			113				Provision for (benefit from) income taxes
	$	(2	)	$	(200	)		Net of tax
¹ Production-related benefits and workers' compensation costs are included in costs to produce coal. See Note 14, "Workers' Compensation Expense" and Note 15 "Employee Benefit Plans" for more information about pension, postretirement and postemployment benefit costs.
2 The gains and losses on sales of available-for-sale-securities are determined on a specific identification basis.

- 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.

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+ Details

Impairment Charges	9 Months Ended
Impairment Charges	Sep. 30, 2013
Impairment charges [Abstract]
Asset Impairment Charges [Text Block]	Impairment charges Weak thermal coal markets in Appalachia are expected to persist longer than the Company previously anticipated, which caused the Company to assess in the third quarter of 2013 whether the carrying values of certain assets were recoverable through future cash flows. The Company determined that the carrying amounts of certain assets associated with the Hazard mining complex in Kentucky and the Company's ADDCAR subsidiary, which manufactures and sells its patented highwall mining system, could not be recovered through future cash flows expected to be generated from use of the assets and their ultimate disposal. The assets' fair values were determined based on projections of cash flows to be generated from use of the assets and their ultimate disposal including estimates relating to market demand, coal prices, production costs and mine plans, and recovery value of the assets. An impairment loss of $142.8 million was recognized to write the carrying value of the assets to their fair value of $71.3 million. These losses are reflected on the line "Asset impairment and mine closure costs" in the condensed consolidated statements of operations. During the third quarter of 2013, the Company also recognized an other-than-temporary impairment of an equity method investment. See further discussion in Note 8, "Equity Method Investments and Membership Interests in Joint Ventures." In the second quarter of 2012, the closure and idling of mines in Appalachia discussed in Note 1, "Basis of Presentation" resulted in closure costs and impairment charges of $523.4 million that are reflected on the line "Asset impairment and mine closures costs" in the condensed consolidated statements of operations.

Inventories

9 Months Ended

Sep. 30, 2013

Inventory Disclosure [Abstract]

Inventories

Inventories consist of the following:



	September 30		December 31
	2013		2012
	(In thousands)
Coal	$	134,481	$	180,917
Repair parts and supplies	143,763		172,139
Work-in-process	9,165		12,368
	$	287,409	$	365,424

The repair parts and supplies are stated net of an allowance for slow-moving and obsolete inventories of $8.8 million at September 30, 2013 and $13.6 million at December 31, 2012.

Investments in Available-for-Sale Securities

9 Months Ended

Sep. 30, 2013

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 and 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:



	September 30, 2013
										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	$	123,809	$	7	$	(126	)	$	123,690	$	123,690	$	—
Corporate notes and bonds	125,479		21		(466		)	125,034		125,034		—
Equity securities	5,271		10,284		(2,865		)	12,690		—		12,690
Total Investments	$	254,559	$	10,312	$	(3,457	)	$	261,414	$	248,724	$	12,690



	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 that have been owned for less than a year was $167.5 million and $223.3 million at September 30, 2013 and December 31, 2012, respectively. The aggregate fair value of investments with unrealized losses that have been owned for over a year was $51.6 million and $0.4 million at September 30, 2013 and December 31, 2012, respectively.

The debt securities outstanding at September 30, 2013 have maturity dates ranging from the fourth quarter of 2013 through the first quarter of 2015. The Company classifies its investments as current based on the nature of the investments and their availability to provide cash for use in current operations.

- Definition

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

+ References + Details

Equity Investments And Membership Interests In Joint Ventures

9 Months Ended

Sep. 30, 2013

Equity Method Investments and Joint Ventures [Abstract]

Equity Investments and Membership Interests in Joint Ventures

Equity Method Investments and Membership Interests in Joint Ventures

The Company accounts for its investments and membership interests in joint ventures under the equity method of accounting if the Company has the ability to exercise significant influence, but not control, over the entity. Below are the equity method investments reflected in the condensed consolidated balance sheets:



In thousands	Knight Hawk			DKRW			DTA			Tenaska			Millennium			Tongue River			Total
Balance at December 31, 2012	$	149,063		$	15,515		$	15,462		$	15,264		$	32,214		$	14,697		$	242,215
Advances to (distributions from) affiliates, net	(5,342		)	—			2,537			—			4,954			2,696			4,845
Equity in comprehensive income (loss)	13,362			(1,832		)	(3,855		)	—			(1,953		)	(281		)	5,441
Impairment of equity investment	—			(13,683		)	—			(15,264		)	—			—			(28,947		)
Balance at September 30, 2013	$	157,083		$	—		$	14,144		$	—		$	35,215		$	17,112		$	223,554

Equity method investments are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the investments may not be recoverable. Certain of the Company's investments are in development stage companies whose success depends on factors including receipt of permits and other regulatory environment issues, the ability of the investee companies to raise additional funds in financial markets that can be volatile, and other key business factors.

During the second quarter of 2013, Tenaska Trailblazer Partners, LLC ("Tenaska") announced that it was discontinuing its development plans for the Trailblazer Energy Center in Texas. As a result, the Company recorded a $20.5 million impairment charge, which consisted of its 35% equity investment of $15.3 million and a $5.2 million receivable balance related to reimbursements for development work.

DKRW Advanced Fuels, LLC ("DKRW") had previously entered into an Engineering, Procurement and Construction Agreement with a Chinese company to construct and commission the Medicine Bow coal-to-liquids facility. The project did not progress to the next stage of development, and the Company recorded an other-than-temporary impairment charge of $57.7 million in the third quarter of 2013, which includes the Company's 24% equity investment of $13.7 million and a $44.0 million loan receivable balance. The impairment charges are included on the line "Asset impairment and mine closure costs" in the condensed consolidated statement of operations.

The Company may be required to make future contingent payments of up to $58.5 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 the achievement of project development milestones, which can be affected by the factors named above.

Derivatives

9 Months Ended

Sep. 30, 2013

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. At September 30, 2013, the Company had protected the price of approximately 94% of its expected purchases for the remainder of 2013 and 82% of its expected 2014 purchases. At September 30, 2013, the Company had purchased heating oil call options for approximately 65 million gallons for the purpose of managing the price risk associated with future diesel purchases.

The Company has also purchased heating oil call options to manage the price risk associated with fuel surcharges on its barge and rail shipments, which cover increases in diesel fuel prices for the respective carriers. At September 30, 2013, the Company held heating oil call options for 2.8 million gallons that will settle in the remainder of 2013 and 3.8 million gallons that will settle ratably in 2014 for the purpose of managing the fluctuations in cash flows associated with fuel surcharges on future shipments.

These positions reduce the Company’s risk of cash flow fluctuations related to these surcharges but the positions are not accounted for as hedges.

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 September 30, 2013, 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	2,314	4,458	780	7,552
Coal purchases	609	1,260	—	1,869

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 $0.4 million of gains in the remainder of 2013 and $7.0 million of gains in 2014.

Tabular derivatives disclosures

The Company has master netting agreements with all of its counterparties which 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 condensed 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 condensed consolidated balance sheets. The fair value and location of derivatives reflected in the accompanying condensed consolidated balance sheets are as follows:



	September 30, 2013								December 31, 2012
Fair Value of Derivatives	Asset			Liability					Asset			Liability
(In thousands)	Derivative			Derivative					Derivative			Derivative
Derivatives Designated as Hedging Instruments
Coal	$	3,009		$	(4	)			$	3,277		$	(10	)

Derivatives Not Designated as Hedging Instruments
Heating oil -- diesel purchases	3,825			—					7,379			—
Heating oil -- fuel surcharges	400			—					1,961			—
Coal -- held for trading purposes	59,789			(52,383		)			17,403			(16,933		)
Coal -- risk management	15,907			(3,903		)			24,843			(7,342		)
Total	79,921			(56,286		)			51,586			(24,275		)
Total derivatives	82,930			(56,290		)			54,863			(24,285		)
Effect of counterparty netting	(55,869		)	55,869					(22,548		)	22,548
Net derivatives as classified in the balance sheets	$	27,061		$	(421	)	$	26,640	$	32,315		$	(1,737	)	$	30,578



		September 30, 2013			December 31, 2012
Net derivatives as reflected on the balance sheets
Heating oil	Other current assets	$	4,225		$	9,340
Coal	Coal derivative assets	22,836			22,975
	Coal derivative liabilities	(421		)	(1,737		)
		$	26,640		$	30,578

The Company had a current liability for the obligation to post cash collateral of $4.9 million at September 30, 2013 and a current asset for the right to reclaim cash collateral of $16.2 million at December 31, 2012. These amounts are not included with the derivatives presented in the table above and are included in "accrued expenses and other current liabilities" and “other current assets”, respectively, in the accompanying condensed consolidated balance sheets.

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

Derivatives used in Cash Flow Hedging Relationships (in thousands)

For the three months ended September 30,



		Gain (Loss) Recognized in Other Comprehensive Income(Effective Portion)						Gains (Losses) Reclassified from Other Comprehensive Income into Income (Effective Portion)
		2013			2012			2013			2012
Coal sales	⁽¹⁾	$	3,132		$	259		$	911		$	542
Coal purchases	⁽²⁾	(942		)	(178		)	(123		)	—
Totals		$	2,190		$	81		$	788		$	542

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 three month periods ended September 30, 2013 and 2012.

Derivatives Not Designated as Hedging Instruments (in thousands)

For the three months ended September 30,



		Gain (Loss) Recognized
		2013			2012
Coal — unrealized	⁽³⁾	$	(10,668	)	$	(11,328	)
Coal — realized	⁽⁴⁾	$	9,929		$	14,072
Heating oil — diesel purchases	⁽⁴⁾	$	(288	)	$	5,184
Heating oil — fuel surcharges	⁽⁴⁾	$	(222	)	$	1,092

____________________________________________________________

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

Derivatives used in Cash Flow Hedging Relationships (in thousands)

For the nine months ended September 30



		Gain (Loss) Recognized in Other Comprehensive Income(Effective Portion)						Gains (Losses) Reclassified from Other Comprehensive Income into Income (Effective Portion)
		2013			2012			2013			2012
Coal sales	⁽¹⁾	$	2,308		$	4,983		$	2,822		$	1,552
Coal purchases	⁽²⁾	(511		)	(1,122		)	(633		)	—
Totals		$	1,797		$	3,861		$	2,189		$	1,552

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 nine month periods ended September 30, 2013 and 2012.

Derivatives Not Designated as Hedging Instruments (in thousands)

For the nine months ended September 30



		Gain (Loss) Recognized
		2013			2012
Coal — unrealized	⁽³⁾	$	(5,089	)	$	23,670
Coal — realized	⁽⁴⁾	$	25,725		$	25,901
Heating oil — diesel purchases	⁽⁴⁾	$	(9,760	)	$	(16,902	)
Heating oil — fuel surcharges	⁽⁴⁾	$	(817	)	$	(1,140	)

____________________________________________________________

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 $0.9 million and $5.5 million during the three months ended September 30, 2013 and 2012, respectively, related to its trading portfolio. The Company recognized net unrealized and realized gains of $3.0 million and $6.2 million during the nine months ended September 30, 2013 and 2012, 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 condensed 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 September 30, 2013, gains on derivative contracts designated as hedge instruments in cash flow hedges of approximately $2.9 million are expected to be reclassified from other comprehensive income into earnings during the next twelve months.

- Definition

The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 14: http://www.xbrl.org/2003/role/presentationRef
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+ Details

Debt

9 Months Ended

Sep. 30, 2013

Debt Disclosure [Abstract]

Debt



	September 30,		December 31,
	2013		2012
	(In thousands)
Term loan ($1.63 billion face value) due 2018	$	1,617,097	$	1,627,384
8.75% senior notes ($600.0 million face value) due 2016	592,646		590,999
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	361,779		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	25,912		40,350
	5,097,434		5,118,775
Less current maturities of debt	23,050		32,896
Long-term debt	$	5,074,384	$	5,085,879

At September 30, 2013, the available borrowing capacity under the Company's lines of credit was approximately $204.0 million.

Fair Value Measurements

9 Months Ended

Sep. 30, 2013

Fair Value Disclosures [Abstract]

Fair Value Measurements

The hierarchy of fair value measurements assigns a level to fair value measurements based on the inputs used in the respective valuation techniques. 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 September 30, 2013.

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



	Fair Value at September 30, 2013
	Total		Level 1		Level 2		Level 3
	(In thousands)
Assets:
Investments in marketable securities	$	261,414	$	101,338	$	160,076	$	—
Derivatives	27,061		22,750		—		4,311
Total assets	$	288,475	$	124,088	$	160,076	$	4,311
Liabilities:
Derivatives	$	421	$	—	$	204	$	217

The Company’s contracts with 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 condensed 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.



	Three Months Ended September 30, 2013			Nine Months Ended September 30, 2013
	(In thousands)
Balance, beginning of period	$	3,438		$	8,174
Realized and unrealized losses recognized in earnings, net	(570		)	(9,882		)
Purchases	1,464			7,317
Issuances	—			(25		)
Settlements	(238		)	(1,490		)
Ending balance	$	4,094		$	4,094

Net unrealized losses during the three and nine month periods ended September 30, 2013 related to level 3 financial instruments held on September 30, 2013 were $0.2 million and $4.8 million, respectively.

Fair Value of Long-Term Debt

At September 30, 2013 and December 31, 2012, the fair value of the Company’s debt, including amounts classified as current, was $4.5 billion and $5.0 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 + Details

Accrued Expenses and Other Current Liabilities

9 Months Ended

Sep. 30, 2013

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:



	September 30,		December 31,
	2013		2012
	(In thousands)
Payroll and employee benefits	$	68,245	$	72,405
Taxes other than income taxes	113,872		121,029
Interest	80,454		42,413
Acquired sales contracts	14,461		14,038
Workers’ compensation	12,215		10,371
Asset retirement obligations	38,895		38,920
Other	20,891		18,842
	$	349,033	$	318,018

Stock-Based Compensation And Other Incentive Plans	9 Months Ended
Stock-Based Compensation And Other Incentive Plans	Sep. 30, 2013
Share-based Compensation [Abstract]
Stock-Based Compensation And Other Incentive Plans	Stock-Based Compensation and Other Incentive Plans The Company granted options to purchase approximately 2.0 million shares of common stock during the nine months ended September 30, 2013. The weighted average exercise price of the options was $5.23 per share and the weighted average grant date fair value was $2.37 per share. The options’ fair value was determined using the Black-Scholes option pricing model, using a weighted average risk-free rate of 0.65%, a weighted average dividend yield of 2.30% and a weighted average volatility of 66.74%. The options’ expected life is 4.5 years and the options vest ratably over three years and provide for the continuation of vesting after retirement for recipients that meet certain criteria. The expense for these options will be recognized through the date that the employee first becomes eligible to retire and is no longer required to provide service to earn all or part of the award. During the nine months ended September 30, 2013, the Company also granted restricted stock units totaling 969,100 shares whose grant date fair value was $5.20 per share. The shares vest at the end of three years. 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. Amounts accrued and unpaid for all grants under the plan totaled $15.0 million and $13.1 million as of September 30, 2013 and December 31, 2012, respectively.

Workers' Compensation Expense

9 Months Ended

Sep. 30, 2013

Workers' Compensation Expense [Abstract]

Workers' Compensation Expense

Workers’ Compensation Expense

The following table details the components of workers’ compensation expense:



	Three Months Ended September 30,				Nine Months Ended September 30,
	2013		2012		2013		2012
	(In thousands)
Service cost	$	363	$	419	$	1,373	$	1,458
Interest cost	709		629		2,022		1,708
Net amortization	262		—		731		(574		)
Curtailments	816		—		816		1,933
Total occupational disease	2,150		1,048		4,942		4,525
Traumatic injury claims and assessments	4,114		7,453		16,263		19,052
Total workers’ compensation expense	$	6,264	$	8,501	$	21,205	$	23,577

Employee Benefit Plans

9 Months Ended

Sep. 30, 2013

Pension and Other Postretirement Benefit Expense [Abstract]

Employee Benefit Plans

. Employee Benefit Plans

The following table details the components of pension benefit costs (credits):



	Three Months Ended September 30,						Nine Months Ended September 30,
	2013			2012			2013			2012
	(In thousands)
Service cost	$	6,672		$	6,156		$	21,162		$	21,062
Interest cost	3,994			3,683			11,796			11,755
Curtailments	47			—			47			324
Expected return on plan assets	(5,848		)	(5,508		)	(17,690		)	(16,523		)
Amortization of prior service costs (credits)	(51		)	273			(152		)	200
Amortization of other actuarial losses	3,617			3,248			12,430			11,019
Net benefit cost	$	8,431		$	7,852		$	27,593		$	27,837

The following table details the components of other postretirement benefit costs (credits):



	Three Months Ended September 30,						Nine Months Ended September 30,
	2013			2012			2013			2012
	(In thousands)
Service cost	$	497		$	541		$	1,591		$	1,629
Interest cost	427			508			1,273			1,519
Curtailments	(5,444		)	(2,212		)	(5,444		)	(4,049		)
Amortization of prior service credits	(2,641		)	(2,837		)	(8,121		)	(8,708		)
Amortization of other actuarial losses (gains)	(55		)	(130		)	(53		)	(391		)
Net benefit credit	$	(7,216	)	$	(4,130	)	$	(10,754	)	$	(10,000	)

A curtailment was triggered in the third quarter of 2013 by reductions in employees' expected years of future service resulting primarily from the sale of Canyon Fuel. Curtailments include the recognition of unamortized prior service costs and actuarial adjustments to the respective projected benefit obligations for the cash balance pension and medical plans and pneumoconiosis benefits.

Earnings Per Common Share	9 Months Ended
Earnings Per Common Share	Sep. 30, 2013
Earnings Per Share [Abstract]
Earnings Per Common Share	. Earnings (Loss) Per Common Share The effect of options, restricted stock and restricted stock units equaling 7.0 million and 5.8 million shares of common stock were excluded from the calculation of diluted weighted average shares outstanding for the three month periods ended September 30, 2013 and 2012, respectively, and 7.9 million and 5.0 million shares were excluded for the nine month periods ended September 30, 2013 and 2012, respectively, because the exercise price or grant price of the securities exceeded the average market price of the Company's common stock for these periods. The weighted average share impacts of options, restricted stock and restricted stock units that were excluded from the calculation of weighted average shares due to the Company's incurring a net loss for the three and nine month periods ended September 30, 2013 and the nine months ended September 30,2012 were not significant.

Settlement with Patriot Coal	9 Months Ended
Settlement with Patriot Coal	Sep. 30, 2013
Settlement with Patriot Coal [Abstract]
Legal Matters and Contingencies [Text Block]	Settlement with Patriot Coal 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. The Company entered into a settlement agreement with Patriot on October, 10, 2013 that resolves all pending and potential legal claims with Patriot stemming from the sale of coal companies to Magnum and the subsequent purchase of those companies by Patriot in 2008. The Company will pay $5.0 million in cash to Patriot upon its exit from bankruptcy, which is reflected in "Other operating income, net" in the condensed consolidated statement of operations for the three month and nine month periods ended September 30, 2013. Additionally, the settlement includes the release of a $16.7 million letter of credit posted by Patriot in the Company's favor for surety bonds related to the companies sold to Magnum. The Company has also agreed to purchase Patriot's Guffey reserves for $16.0 million in cash upon their exit from bankruptcy. The Guffey reserves border the Company's Leer metallurgical coal development.

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2013
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Commitments and Contingencies The Company accrues for cost related to contingencies when a loss is probable and the amount is reasonably determinable. Disclosure of contingencies is included in the financial statements when it is at least reasonably possible that a material loss or an additional material loss in excess of amounts already accrued may be incurred. 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. The Company'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 million and $377 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 damages calculations were significantly inflated because it did not seek to determine damages as of the time of the breach and in some instances artificially assumed future nondelivery 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. The trial court awarded total damages and interest in the amount of $104.1 million, which consisted of $13.8 million for past damages, and $90.3 million for future damages. 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. On August 13, 2012, the Superior Court of Pennsylvania affirmed the award of past damages, but ruled that the lower court should have calculated future damages as of the date of breach, and remanded the matter back to the lower court with instructions to recalculate that portion of the award. 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. On July 2, 2013, the Supreme Court of Pennsylvania denied the Petition of Allowance. As this action finalized the past damage award, Wolf Run paid $15.6 million for the past damage amount, including interest, to Allegheny in July 2013. The future damage award is now back before the lower court, but no hearing dates have been set at this time. In addition, the Company is a party to numerous claims and lawsuits with respect to various matters. As of September 30, 2013 and December 31, 2012, the Company had accrued $21.2 million and $32.8 million, respectively, for all legal matters, including $7.7 million and $4.4 million, respectively, 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.

Segment Information

9 Months Ended

Sep. 30, 2013

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 or type 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 WBIT segment, with operations in Colorado; the Appalachia (APP) segment, with operations in West Virginia, Kentucky, Maryland and Virginia. The “Other” operating segment includes primarily the Company’s Illinois operations and ADDCAR.

Operating segment results for the three and nine months ended September 30, 2013 and 2012 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. 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 operating segment results for the WBIT segment for all periods presented reflect only continuing operations, since Canyon Fuel results are classified as discontinued operations in the condensed consolidated statements of operations.

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. Asset balances for the WBIT segment as of September 30, 2012 include the Canyon Fuel assets. Prior year asset amounts have been restated to reflect a change in how certain unassigned coal reserves and goodwill amounts are presented.



	PRB			APP			WBIT		Other Operating Segments			Corporate, Other and Eliminations			Consolidated
	(in thousands)
Three months ended September 30, 2013
Revenues	$	420,521		$	263,188		$	78,022	$	29,538		$	—		$	791,269
Income (loss) from operations	20,694			(157,883		)	9,287		(9,231		)	(97,620		)	(234,753		)
Depreciation, depletion and amortization	46,619			46,529			9,436		2,523			1,216			106,323
Amortization of acquired sales contracts, net	(864		)	(2,691		)	—		987			—			(2,568		)
Asset impairment and mine closure costs	—			126,449			—		16,280			57,668			200,397
Capital expenditures	1,695			44,624			5,859		1,263			663			54,104

Three months ended September 30, 2012
Revenues	$	406,719		$	436,409		$	105,515	$	26,527		$	—		$	975,170
Income (loss) from operations	38,873			88,695			24,110		(1,298		)	(31,138		)	119,242
Depreciation, depletion and amortization	43,944			61,596			9,985		2,594			823			118,942
Amortization of acquired sales contracts, net	(589		)	(3,711		)	—		207			—			(4,093		)
Asset impairment and mine closure costs	—			(1,801		)	—		(210		)	(133		)	(2,144		)
Capital expenditures	5,620			77,772			13,510		3,640			1,353			101,895

Nine months ended September 30, 2013
Revenues	$	1,135,892		$	883,484		$	187,374	$	88,221		$	—		$	2,294,971
Income (loss) from operations	53,244			(190,278		)	23,766		(407		)	(208,788		)	(322,463		)
Depreciation, depletion and amortization	130,993			157,866			26,528		7,792			4,422			327,601
Amortization of acquired sales contracts, net	(3,004		)	(7,975		)	—		3,392			—			(7,587		)
Asset impairment and mine closure costs	—			126,449			—		16,280			78,150			220,879
Total assets	1,897,218			4,141,072			146,947		137,941			3,208,277			9,531,455
Capital expenditures	5,671			137,390			13,147		4,776			62,184			223,168

Nine months ended September 30, 2012
Revenues	$	1,130,408		$	1,409,776		$	272,359	$	88,549		$	—		$	2,901,092
Income (loss) from operations	94,163			(388,563		)	34,937		(3,757		)	(186,634		)	(449,854		)
Depreciation, depletion and amortization	122,298			210,789			29,894		9,704			1,946			374,631
Amortization of acquired sales contracts, net	(1,374		)	(21,658		)	—		471			—			(22,561		)
Asset impairment and mine closure costs	—			524,115			—		(437		)	(239		)	523,439
Total assets	2,234,941			4,130,273			676,057		169,981			2,724,602			9,935,854
Capital expenditures	15,399			222,177			42,761		8,153			15,478			303,968

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



	Three Months Ended September 30,						Nine Months Ended September 30,
	2013			2012			2013			2012
	(In thousands)
Income (loss) from operations	$	(234,753	)	$	119,242		$	(322,463	)	$	(449,854	)
Interest expense	(95,624		)	(75,710		)	(285,454		)	(229,210		)
Interest and investment income	697			1,459			4,749			3,568
Other nonoperating expense	$	—		$	—		$	—		$	(19,042	)
Income (loss) from continuing operations before income taxes	$	(329,680	)	$	44,991		$	(603,168	)	$	(694,538	)

- 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
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8981-108599

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
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-Topic 280
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9031-108599

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 42
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
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Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8924-108599

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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+ Details

Supplemental Condensed Consolidating Financial Information

9 Months Ended

Sep. 30, 2013

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 United States):

Condensed Consolidating Statements of Operations

Three Months Ended September 30, 2013



	Parent/Issuer			Guarantor Subsidiaries			Non- Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Revenues	$	—		$	791,269		$	—		$	—		$	791,269
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	169			688,543			—			—			688,712
Depreciation, depletion and amortization	1,549			104,765			9			—			106,323
Amortization of acquired sales contracts, net	—			(2,568		)	—			—			(2,568		)
Change in fair value of coal derivatives and coal trading activities, net	—			9,753			—			—			9,753
Asset impairment and mine closure costs	57,668			142,729			—			—			200,397
Selling, general and administrative expenses	19,104			8,214			1,482			—			28,800
Other operating income, net	2,345			(7,740		)	—			—			(5,395		)
	80,835			943,696			1,491			—			1,026,022
Loss from investment in subsidiaries	(61,537		)	—			—			61,537			—
Loss from operations	(142,372		)	(152,427		)	(1,491		)	61,537			(234,753		)
Interest expense, net
Interest expense	(114,536		)	(6,222		)	(1,070		)	26,204			(95,624		)
Interest and investment income	6,606			18,975			1,320			(26,204		)	697
	(107,930		)	12,753			250			—			(94,927		)

Loss from continuing operations before income taxes	(250,302		)	(139,674		)	(1,241		)	61,537			(329,680		)
Provision for (benefit from) income taxes	(121,939		)	—			26			—			(121,913		)
Loss from continuing operations	(128,363		)	(139,674		)	(1,267		)	61,537			(207,767		)
Income from discontinued operations, including gain on sale - net of tax	—			79,404			—			—			79,404
Net loss	$	(128,363	)	$	(60,270	)	$	(1,267	)	$	61,537		$	(128,363	)
Total comprehensive loss	$	(125,996	)	$	(59,241	)	$	(1,267	)	$	60,508		$	(125,996	)

Condensed Consolidating Statements of Operations

Nine Months Ended September 30, 2013



	Parent/Issuer			Guarantor Subsidiaries			Non- Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Revenues	$	—		$	2,294,971		$	—		$	—		$	2,294,971
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	4,881			1,989,772			—			—			1,994,653
Depreciation, depletion and amortization	4,430			323,144			27			—			327,601
Amortization of acquired sales contracts, net	—			(7,587		)	—			—			(7,587		)
Change in fair value of coal derivatives and coal trading activities, net	—			2,053			—			—			2,053
Asset impairment and mine closure costs	78,150			142,729			—			—			220,879
Selling, general and administrative expenses	63,006			28,978			4,327			—			96,311
Other operating income, net	(4,663		)	(10,704		)	(1,109		)	—			(16,476		)
	145,804			2,468,385			3,245			—			2,617,434
Loss from investment in subsidiaries	(42,199		)	—			—			42,199			—
Loss from operations	(188,003		)	(173,414		)	(3,245		)	42,199			(322,463		)
Interest expense, net
Interest expense	(336,310		)	(18,502		)	(3,170		)	72,528			(285,454		)
Interest and investment income	22,917			49,986			4,374			(72,528		)	4,749
	(313,393		)	31,484			1,204			—			(280,705		)

Loss from continuing operations before income taxes	(501,396		)	(141,930		)	(2,041		)	42,199			(603,168		)
Provision for (benefit from) income taxes	(230,778		)	—			44			—			(230,734		)
Loss from continuing operations	(270,618		)	(141,930		)	(2,085		)	42,199			(372,434		)
Income from discontinued operations, including gain on sale - net of tax	—			101,816			—			—			101,816
Net loss	$	(270,618	)	$	(40,114	)	$	(2,085	)	$	42,199		$	(270,618	)
Total comprehensive loss	$	(262,717	)	$	(39,175	)	$	(2,085	)	$	41,260		$	(262,717	)

Condensed Consolidating Statements of Operations

Three Months Ended September 30, 2012



	Parent/Issuer			Guarantor Subsidiaries			Non- Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Revenues	$	—		$	975,170		$	—		$	—		$	975,170
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	2,437			806,052			—			—			808,489
Depreciation, depletion and amortization	1,399			117,534			9			—			118,942
Amortization of acquired sales contracts, net	—			(4,093		)	—			—			(4,093		)
Change in fair value of coal derivatives and coal trading activities, net	—			5,840			—			—			5,840
Asset impairment and mine closure costs	—			(2,144		)	—			—			(2,144		)
Legal contingencies	—			(79,532		)	—			—			(79,532		)
Selling, general and administrative expenses	22,051			9,432			1,783			—			33,266
Other operating income, net	(11,052		)	(13,699		)	(89		)	—			(24,840		)
	14,835			839,390			1,703			—			855,928
Income from investment in subsidiaries	164,152			—			—			(164,152		)	—
Income (loss) from operations	149,317			135,780			(1,703		)	(164,152		)	119,242
Interest expense, net
Interest expense	(91,577		)	(6,870		)	(649		)	23,386			(75,710		)
Interest and investment income	8,329			14,570			1,946			(23,386		)	1,459
	(83,248		)	7,700			1,297			—			(74,251		)

Income (loss) from continuing operations before income taxes	66,069			143,480			(406		)	(164,152		)	44,991
Provision for income taxes	20,318			—			—			—			20,318
Income (loss) from continuing operations	45,751			143,480			(406		)	(164,152		)	24,673
Income from discontinued operations, net of tax	—			21,078			—			—			21,078
Net income (loss)	$	45,751		$	164,558		$	(406	)	$	(164,152	)	$	45,751
Total comprehensive income (loss)	$	44,299		$	163,375		$	(406	)	$	(162,969	)	$	44,299

Condensed Consolidating Statements of Operations

Nine Months Ended September 30, 2012



	Parent/Issuer			Guarantor Subsidiaries			Non- Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Revenues	$	—		$	2,901,092		$	—		$	—		$	2,901,092
Costs, expenses and other													—
Cost of sales (exclusive of items shown separately below)	7,694			2,406,612			—			—			2,414,306
Depreciation, depletion and amortization	3,959			370,648			24			—			374,631
Amortization of acquired sales contracts, net	—			(22,561		)	—			—			(22,561		)
Change in fair value of coal derivatives and coal trading activities, net	—			(29,827		)	—			—			(29,827		)
Asset impairment and mine closure costs	—			523,439			—			—			523,439
Goodwill impairment	—			115,791			—			—			115,791
Legal contingencies	—			(79,532		)	—			—			(79,532		)
Selling, general and administrative expenses	62,469			30,965			5,871			—			99,305
Other operating income, net	(7,693		)	(23,811		)	(13,102		)	—			(44,606		)
	66,429			3,291,724			(7,207		)	—			3,350,946
Loss from investment in subsidiaries	(324,429		)	—			—			324,429			—
Income (loss) from operations	(390,858		)	(390,632		)	7,207			324,429			(449,854		)
Interest expense, net
Interest expense	(263,381		)	(27,285		)	(2,382		)	63,838			(229,210		)
Interest and investment income	19,087			42,508			5,811			(63,838		)	3,568
	(244,294		)	15,223			3,429			—			(225,642		)
Other non-operating expense
Net loss resulting from early retirement of ICG debt	(17,349		)	(1,693		)	—			—			(19,042		)

Income (loss) from continuing operations before income taxes	(652,501		)	(377,102		)	10,636			324,429			(694,538		)
Provision for (benefit from) income taxes	(264,237		)	—			1,581			—			(262,656		)
Income (loss) from continuing operations	(388,264		)	(377,102		)	9,055			324,429			(431,882		)
Income from discontinued operations, net of tax	—			43,618			—			—			43,618
Net Income (loss)	(388,264		)	(333,484		)	9,055			324,429			(388,264		)
Less: Net income attributable to noncontrolling interest	(268		)	—			—			—			(268		)
Net Income (loss) attributable to Arch Coal, Inc.	$	(388,532	)	$	(333,484	)	$	9,055		$	324,429		$	(388,532	)
Total comprehensive income (loss)	$	(385,523	)	$	(336,648	)	$	9,055		$	327,593		$	(385,523	)

Condensed Consolidating Balance Sheets

September 30, 2013



	Parent/Issuer		Guarantor Subsidiaries		Non-Guarantor Subsidiaries		Eliminations			Consolidated
	(In thousands)
Assets
Cash and cash equivalents	$	1,021,245	$	100,410	$	11,473	$	—		$	1,133,128
Restricted cash	—		—		—		—			—
Short term investments	248,724		—		—		—			248,724
Receivables	7,847		21,178		190,493		(4,679		)	214,839
Inventories	—		287,409		—		—			287,409
Other	96,992		48,270		277		—			145,539
Total current assets	1,374,808		457,267		202,243		(4,679		)	2,029,639

Property, plant and equipment, net	25,526		6,752,687		46		(34		)	6,778,225

Investment in subsidiaries	7,992,601		—		—		(7,992,601		)	—
Intercompany receivables	—		1,986,992		—		(1,986,992		)	—
Note receivable from Arch Western	675,000		—		—		(675,000		)	—
Other	147,950		575,551		90		—			723,591
Total other assets	8,815,551		2,562,543		90		(10,654,593		)	723,591
Total assets	$	10,215,885	$	9,772,497	$	202,379	$	(10,659,306	)	$	9,531,455

Liabilities and Stockholders’ Equity
Accounts payable	$	20,728	$	186,468	$	77	$	—		$	207,273
Accrued expenses and other current liabilities	107,756		246,063		314		(4,679		)	349,454
Current maturities of debt	19,343		3,707		—		—			23,050
Total current liabilities	147,827		436,238		391		(4,679		)	579,777
Long-term debt	5,055,021		19,363		—		—			5,074,384
Intercompany payables	1,810,718		—		176,274		(1,986,992		)	—
Note payable to Arch Coal	—		675,000		—		(675,000		)	—
Asset retirement obligations	1,150		409,971		—		—			411,121
Accrued pension benefits	36,304		32,235		—		—			68,539
Accrued postretirement benefits other than pension	14,267		30,012		—		—			44,279
Accrued workers’ compensation	25,601		56,413		—		—			82,014
Deferred income taxes	484,130		—		—		—			484,130
Other noncurrent liabilities	59,179		146,055		323		—			205,557
Total liabilities	7,634,197		1,805,287		176,988		(2,666,671		)	6,949,801
Stockholders’ equity	2,581,688		7,967,210		25,391		(7,992,635		)	2,581,654
Total liabilities and stockholders’ equity	$	10,215,885	$	9,772,497	$	202,379	$	(10,659,306	)	$	9,531,455

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	—		1,600,311		—		(1,600,311		)	—
Note receivable from Arch Western	675,000		—		—		(675,000		)	—
Other	187,171		568,314		90		—			755,575
Total other assets	9,116,679		2,168,625		90		(10,529,819		)	755,575
Total assets	$	10,209,293	$	10,071,396	$	260,731	$	(10,534,643	)	$	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	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
Intercompany payables	1,367,739		—		232,572		(1,600,311		)	—
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	7,354,726		1,844,360		233,259		(2,280,135		)	7,152,210
Stockholders’ equity	2,854,567		8,227,036		27,472		(8,254,508		)	2,854,567
Total liabilities and stockholders’ equity	$	10,209,293	$	10,071,396	$	260,731	$	(10,534,643	)	$	10,006,777

Condensed Consolidating Statements of Cash Flows

Nine Months Ended September 30, 2013



	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$	(22,206	)	$	153,868		$	54,930		$	—		$	186,592
Investing Activities
Capital expenditures	(2,488		)	(220,680		)	—			—			(223,168		)
Minimum royalty payments	—			(10,901		)	—			—			(10,901		)
Proceeds from dispositions of property, plant and equipment	—			8,799			—			—			8,799
Proceeds from sales-leaseback transactions	—			34,919			—			—			34,919
Proceeds from sale of Canyon Fuel	—			422,663			—			—			422,663
Purchases of short term investments	(85,418		)	—			—			—			(85,418		)
Proceeds from sales of short term investments	67,255			—			—			—			67,255
Investments in and advances to affiliates	(4,016		)	(7,492		)	—			384			(11,124		)
Change in restricted cash	3,453			—			—			—			3,453
Cash provided by (used in) investing activities	(21,214		)	227,308			—			384			206,478
Financing Activities
Contributions from parent	—			384			—			(384		)	—
Payments on term loan	(12,375		)	—			—			—			(12,375		)
Payments to retire debt	—			(384		)	—			—			(384		)
Net payments on other debt	(12,700		)	—			—			—			(12,700		)
Dividends paid	(19,105		)	—			—			—			(19,105		)
Transactions with affiliates, net	437,532			(381,234		)	(56,298		)	—			—
Cash provided by (used in) financing activities	393,352			(381,234		)	(56,298		)	(384		)	(44,564		)
Increase (decrease) in cash and cash equivalents	349,932			(58		)	(1,368		)	—			348,506
Cash and cash equivalents, beginning of period	671,313			100,468			12,841			—			784,622
Cash and cash equivalents, end of period	$	1,021,245		$	100,410		$	11,473		$	—		$	1,133,128

Condensed Consolidating Statements of Cash Flows

Nine Months Ended September 30, 2012



	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$	(610,129	)	$	874,545		$	91,979		$	—		$	356,395
Investing Activities
Capital expenditures	(4,150		)	(299,818		)	—			—			(303,968		)
Minimum royalty payments	—			(9,192		)	—			—			(9,192		)
Proceeds from dispositions of property, plant and equipment	—			1,127			21,497			—			22,624
Purchases of short term investments	(99,628		)	—			—			—			(99,628		)
Investments in and advances to affiliates	(5,138		)	(9,082		)	—			1,535			(12,685		)
Purchase of noncontrolling interest	—			(17,500		)	—			—			(17,500		)
Change in restricted cash	6,872			—			—			—			6,872
Cash provided by (used in) investing activities	(102,044		)	(334,465		)	21,497			1,535			(413,477		)
Financing Activities
Contributions from parent	—			1,535			—			(1,535		)	—
Proceeds from issuance of term loan	1,386,000			—			—			—			1,386,000
Payments on term loan	(3,500		)	—			—			—			(3,500		)
Payments to retire debt	—			(452,806		)	—			—			(452,806		)
Net decrease in borrowings under lines of credit	(375,000		)	—			(6,300		)	—			(381,300		)
Net payments from other debt	(13,078		)	—			—			—			(13,078		)
Debt financing costs	(34,640		)	—			(46		)	—			(34,686		)
Dividends paid	(36,072		)	—			—			—			(36,072		)
Proceeds from exercise of options under incentive plans	5,131			—			—			—			5,131
Transactions with affiliates, net	30,338			66,364			(96,702		)	—			—
Cash provided by (used in) financing activities	959,179			(384,907		)	(103,048		)	(1,535		)	469,689
Increase in cash and cash equivalents	247,006			155,173			10,428			—			412,607
Cash and cash equivalents, beginning of period	66,542			70,258			1,349			—			138,149
Cash and cash equivalents, end of period	$	313,548		$	225,431		$	11,777		$	—		$	550,756

Basis of Presentation (Policy)	9 Months Ended
Basis of Presentation (Policy)	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	The accompanying unaudited condensed 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 steel producers both in the United States and around the world. The Company currently operates mining complexes in West Virginia, Kentucky, Maryland, Virginia, Illinois, Wyoming and Colorado. In addition, the Company is developing a metallurgical coal mine in West Virginia. All subsidiaries are wholly-owned. Intercompany transactions and accounts have been eliminated in consolidation. The Company completed the sale of a subsidiary comprised of three mining complexes in the Western Bituminous reportable segment ("WBIT") on August 16, 2013. The results of these mining complexes have been segregated from continuing operations and are reflected, net of tax, as discontinued operations in the condensed consolidated statements of operations for all periods presented. See further discussion in Note 3, "Discontinued Operations". In response to decreasing demand for thermal coal in Appalachia, the Company closed four mining complexes, temporarily idled a fifth complex, and curtailed production at other mines in the region in the second quarter of 2012. The operations continued to ship from inventory into the third quarter of 2012. The results for the closed and idled complexes are reflected in continuing operations in the condensed consolidating statements of operations for the three and nine month periods ended September 30, 2012. See further discussion in Note 5, "Impairment Charges". The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States for interim financial reporting and U.S. Securities and Exchange Commission regulations. In the opinion of management, all adjustments, consisting of normal, recurring accruals considered necessary for a fair presentation, have been included. Results of operations for the three and nine month periods ended September 30, 2013 are not necessarily indicative of results to be expected for the year ending December 31, 2013. These financial statements should be read in conjunction with the audited financial statements and related notes as of and for the year ended December 31, 2012 included in the Company’s Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission.

- Definition

Disclosure of accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example, common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting. The accounting policy may also address the accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary.

+ References + Details

Discontinued Operations (Tables)

9 Months Ended

Sep. 30, 2013

Discontinued Operations and Disposal Groups [Abstract]

ResultsOfDiscontinuedOperationsTableTextBlock [Table Text Block]

The following table summarizes the results of discontinued operations:



	Three Months Ended September 30,					Nine Months Ended September 30,
	2013		2012			2013		2012
	(In thousands)
Total Revenues	$	45,763	$	112,448		$	219,002	$	289,715
Income from discontinued operations before income taxes	$	3,429	$	16,718		$	32,166	$	50,911
Gain on sale	115,679		—			115,679		—
Income tax expense (benefit)	39,704		(4,360		)	46,029		7,293
Income from discontinued operations, including gain on sale - net of tax	$	79,404	$	21,078		$	101,816	$	43,618
Basic earnings per common share from discontinued operations	$	0.37	$	0.10		$	0.48	$	0.21
Diluted earnings per common share from discontinued operations	$	0.37	$	0.10		$	0.48	$	0.21

Accumulated Other Comprehensive Income (Loss) (Tables)

9 Months Ended

Sep. 30, 2013

Accumulated Other Comprehensive Income (Loss) [Abstract]

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

ollowing items are included in accumulated other comprehensive loss:



				Pension,
				Postretirement
				and Other						Accumulated
				Post-						Other
	Derivative			Employment			Available-for-			Comprehensive
	Instruments			Benefits			Sale Securities			Loss
	(In thousands)
Balance at December 31, 2012	$	2,244		$	(18,286	)	$	(465	)	$	(16,507	)
Unrealized gains	1,197			1,938			4,653			7,788
Amounts reclassified from accumulated other comprehensive income	(1,339		)	1,252			200			113
Balance at September 30, 2013	$	2,102		$	(15,096	)	$	4,388		$	(8,606	)

Schedule of comprehensive income reclassifications [Table Text Block]

The following amounts were reclassified out of accumulated other comprehensive loss:



	Amount Reclassified from
	Accumulated Comprehensive Loss							Line Item in the
Details about accumulated other	Three Months Ended			Nine Months Ended				Condensed Consolidated
comprehensive income components	September 30, 2013			September 30, 2013				Statement of Operations
	(In thousands)
Derivative instruments	$	692		$	2,093			Revenues
	(249		)	(754		)		Provision for (benefit from) income taxes
	$	443		$	1,339			Net of tax

Pension, postretirement and other post-employment benefits
Amortization of prior service credits	$	5,573		$	11,154		¹
Amortization of actuarial gains (losses), net	(3,823		)	(13,108		)	¹
	1,750			(1,954		)		Total before tax
	(631		)	702				Provision for (benefit from) income taxes
	$	1,119		$	(1,252	)		Net of tax

Available-for-sale securities	$	(4	)	$	(313	)	²	Interest and investment income
	2			113				Provision for (benefit from) income taxes
	$	(2	)	$	(200	)		Net of tax
¹ Production-related benefits and workers' compensation costs are included in costs to produce coal. See Note 14, "Workers' Compensation Expense" and Note 15 "Employee Benefit Plans" for more information about pension, postretirement and postemployment benefit costs.
2 The gains and losses on sales of available-for-sale-securities are determined on a specific identification basis.

Inventories (Tables)

9 Months Ended

Sep. 30, 2013

Inventory Disclosure [Abstract]

Inventories

Inventories consist of the following:



	September 30		December 31
	2013		2012
	(In thousands)
Coal	$	134,481	$	180,917
Repair parts and supplies	143,763		172,139
Work-in-process	9,165		12,368
	$	287,409	$	365,424

Investments in Available-for-Sale Securities (Tables)

9 Months Ended

Sep. 30, 2013

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:



	September 30, 2013
										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	$	123,809	$	7	$	(126	)	$	123,690	$	123,690	$	—
Corporate notes and bonds	125,479		21		(466		)	125,034		125,034		—
Equity securities	5,271		10,284		(2,865		)	12,690		—		12,690
Total Investments	$	254,559	$	10,312	$	(3,457	)	$	261,414	$	248,724	$	12,690



	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

- 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 + Details

Equity Investments And Membership Interests In Joint Ventures (Tables)

9 Months Ended

Sep. 30, 2013

Equity Method Investments and Joint Ventures [Abstract]

Schedule Of Equity Method Investments



In thousands	Knight Hawk			DKRW			DTA			Tenaska			Millennium			Tongue River			Total
Balance at December 31, 2012	$	149,063		$	15,515		$	15,462		$	15,264		$	32,214		$	14,697		$	242,215
Advances to (distributions from) affiliates, net	(5,342		)	—			2,537			—			4,954			2,696			4,845
Equity in comprehensive income (loss)	13,362			(1,832		)	(3,855		)	—			(1,953		)	(281		)	5,441
Impairment of equity investment	—			(13,683		)	—			(15,264		)	—			—			(28,947		)
Balance at September 30, 2013	$	157,083		$	—		$	14,144		$	—		$	35,215		$	17,112		$	223,554

Derivatives (Tables)

9 Months Ended

Sep. 30, 2013

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Price Risk Derivatives

At September 30, 2013, 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	2,314	4,458	780	7,552
Coal purchases	609	1,260	—	1,869

Disclosure Of Fair Value Of Derivatives



	September 30, 2013								December 31, 2012
Fair Value of Derivatives	Asset			Liability					Asset			Liability
(In thousands)	Derivative			Derivative					Derivative			Derivative
Derivatives Designated as Hedging Instruments
Coal	$	3,009		$	(4	)			$	3,277		$	(10	)

Derivatives Not Designated as Hedging Instruments
Heating oil -- diesel purchases	3,825			—					7,379			—
Heating oil -- fuel surcharges	400			—					1,961			—
Coal -- held for trading purposes	59,789			(52,383		)			17,403			(16,933		)
Coal -- risk management	15,907			(3,903		)			24,843			(7,342		)
Total	79,921			(56,286		)			51,586			(24,275		)
Total derivatives	82,930			(56,290		)			54,863			(24,285		)
Effect of counterparty netting	(55,869		)	55,869					(22,548		)	22,548
Net derivatives as classified in the balance sheets	$	27,061		$	(421	)	$	26,640	$	32,315		$	(1,737	)	$	30,578



		September 30, 2013			December 31, 2012
Net derivatives as reflected on the balance sheets
Heating oil	Other current assets	$	4,225		$	9,340
Coal	Coal derivative assets	22,836			22,975
	Coal derivative liabilities	(421		)	(1,737		)
		$	26,640		$	30,578

Effects Of Derivatives On Measures Of Financial Performance

Derivatives used in Cash Flow Hedging Relationships (in thousands)

For the nine months ended September 30



		Gain (Loss) Recognized in Other Comprehensive Income(Effective Portion)						Gains (Losses) Reclassified from Other Comprehensive Income into Income (Effective Portion)
		2013			2012			2013			2012
Coal sales	⁽¹⁾	$	2,308		$	4,983		$	2,822		$	1,552
Coal purchases	⁽²⁾	(511		)	(1,122		)	(633		)	—
Totals		$	1,797		$	3,861		$	2,189		$	1,552

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 nine month periods ended September 30, 2013 and 2012.

Derivatives Not Designated as Hedging Instruments (in thousands)

For the nine months ended September 30



		Gain (Loss) Recognized
		2013			2012
Coal — unrealized	⁽³⁾	$	(5,089	)	$	23,670
Coal — realized	⁽⁴⁾	$	25,725		$	25,901
Heating oil — diesel purchases	⁽⁴⁾	$	(9,760	)	$	(16,902	)
Heating oil — fuel surcharges	⁽⁴⁾	$	(817	)	$	(1,140	)

____________________________________________________________

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

Derivatives used in Cash Flow Hedging Relationships (in thousands)

For the three months ended September 30,



		Gain (Loss) Recognized in Other Comprehensive Income(Effective Portion)						Gains (Losses) Reclassified from Other Comprehensive Income into Income (Effective Portion)
		2013			2012			2013			2012
Coal sales	⁽¹⁾	$	3,132		$	259		$	911		$	542
Coal purchases	⁽²⁾	(942		)	(178		)	(123		)	—
Totals		$	2,190		$	81		$	788		$	542

Derivatives Not Designated as Hedging Instruments (in thousands)

For the three months ended September 30,



		Gain (Loss) Recognized
		2013			2012
Coal — unrealized	⁽³⁾	$	(10,668	)	$	(11,328	)
Coal — realized	⁽⁴⁾	$	9,929		$	14,072
Heating oil — diesel purchases	⁽⁴⁾	$	(288	)	$	5,184
Heating oil — fuel surcharges	⁽⁴⁾	$	(222	)	$	1,092

____________________________________________________________

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

Debt (Tables)

9 Months Ended

Sep. 30, 2013

Debt Disclosure [Abstract]

Debt



	September 30,		December 31,
	2013		2012
	(In thousands)
Term loan ($1.63 billion face value) due 2018	$	1,617,097	$	1,627,384
8.75% senior notes ($600.0 million face value) due 2016	592,646		590,999
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	361,779		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	25,912		40,350
	5,097,434		5,118,775
Less current maturities of debt	23,050		32,896
Long-term debt	$	5,074,384	$	5,085,879

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2013

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 condensed consolidated balance sheet:



	Fair Value at September 30, 2013
	Total		Level 1		Level 2		Level 3
	(In thousands)
Assets:
Investments in marketable securities	$	261,414	$	101,338	$	160,076	$	—
Derivatives	27,061		22,750		—		4,311
Total assets	$	288,475	$	124,088	$	160,076	$	4,311
Liabilities:
Derivatives	$	421	$	—	$	204	$	217

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.



	Three Months Ended September 30, 2013			Nine Months Ended September 30, 2013
	(In thousands)
Balance, beginning of period	$	3,438		$	8,174
Realized and unrealized losses recognized in earnings, net	(570		)	(9,882		)
Purchases	1,464			7,317
Issuances	—			(25		)
Settlements	(238		)	(1,490		)
Ending balance	$	4,094		$	4,094

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

9 Months Ended

Sep. 30, 2013

Accrued Expenses and Other Current Liabilities [Abstract]

Schedule of Accrued Liabilities [Table Text Block]

Accrued expenses and other current liabilities consist of the following:



	September 30,		December 31,
	2013		2012
	(In thousands)
Payroll and employee benefits	$	68,245	$	72,405
Taxes other than income taxes	113,872		121,029
Interest	80,454		42,413
Acquired sales contracts	14,461		14,038
Workers’ compensation	12,215		10,371
Asset retirement obligations	38,895		38,920
Other	20,891		18,842
	$	349,033	$	318,018

Workers' Compensation Expense (Tables)

9 Months Ended

Sep. 30, 2013

Workers' Compensation Expense [Abstract]

Workers' Compensation Expense



	Three Months Ended September 30,				Nine Months Ended September 30,
	2013		2012		2013		2012
	(In thousands)
Service cost	$	363	$	419	$	1,373	$	1,458
Interest cost	709		629		2,022		1,708
Net amortization	262		—		731		(574		)
Curtailments	816		—		816		1,933
Total occupational disease	2,150		1,048		4,942		4,525
Traumatic injury claims and assessments	4,114		7,453		16,263		19,052
Total workers’ compensation expense	$	6,264	$	8,501	$	21,205	$	23,577

Employee Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2013

Pension and Other Postretirement Benefit Expense [Abstract]

Other Postretirement Benefit Costs Table Text Block [Table Text Block]

The following table details the components of other postretirement benefit costs (credits):



	Three Months Ended September 30,						Nine Months Ended September 30,
	2013			2012			2013			2012
	(In thousands)
Service cost	$	497		$	541		$	1,591		$	1,629
Interest cost	427			508			1,273			1,519
Curtailments	(5,444		)	(2,212		)	(5,444		)	(4,049		)
Amortization of prior service credits	(2,641		)	(2,837		)	(8,121		)	(8,708		)
Amortization of other actuarial losses (gains)	(55		)	(130		)	(53		)	(391		)
Net benefit credit	$	(7,216	)	$	(4,130	)	$	(10,754	)	$	(10,000	)

Pension Benefit Costs



	Three Months Ended September 30,						Nine Months Ended September 30,
	2013			2012			2013			2012
	(In thousands)
Service cost	$	6,672		$	6,156		$	21,162		$	21,062
Interest cost	3,994			3,683			11,796			11,755
Curtailments	47			—			47			324
Expected return on plan assets	(5,848		)	(5,508		)	(17,690		)	(16,523		)
Amortization of prior service costs (credits)	(51		)	273			(152		)	200
Amortization of other actuarial losses	3,617			3,248			12,430			11,019
Net benefit cost	$	8,431		$	7,852		$	27,593		$	27,837

Segment Information (Tables)

9 Months Ended

Sep. 30, 2013

Segment Reporting [Abstract]

Schedule Of Operating Segment Results



	PRB			APP			WBIT		Other Operating Segments			Corporate, Other and Eliminations			Consolidated
	(in thousands)
Three months ended September 30, 2013
Revenues	$	420,521		$	263,188		$	78,022	$	29,538		$	—		$	791,269
Income (loss) from operations	20,694			(157,883		)	9,287		(9,231		)	(97,620		)	(234,753		)
Depreciation, depletion and amortization	46,619			46,529			9,436		2,523			1,216			106,323
Amortization of acquired sales contracts, net	(864		)	(2,691		)	—		987			—			(2,568		)
Asset impairment and mine closure costs	—			126,449			—		16,280			57,668			200,397
Capital expenditures	1,695			44,624			5,859		1,263			663			54,104

Three months ended September 30, 2012
Revenues	$	406,719		$	436,409		$	105,515	$	26,527		$	—		$	975,170
Income (loss) from operations	38,873			88,695			24,110		(1,298		)	(31,138		)	119,242
Depreciation, depletion and amortization	43,944			61,596			9,985		2,594			823			118,942
Amortization of acquired sales contracts, net	(589		)	(3,711		)	—		207			—			(4,093		)
Asset impairment and mine closure costs	—			(1,801		)	—		(210		)	(133		)	(2,144		)
Capital expenditures	5,620			77,772			13,510		3,640			1,353			101,895

Nine months ended September 30, 2013
Revenues	$	1,135,892		$	883,484		$	187,374	$	88,221		$	—		$	2,294,971
Income (loss) from operations	53,244			(190,278		)	23,766		(407		)	(208,788		)	(322,463		)
Depreciation, depletion and amortization	130,993			157,866			26,528		7,792			4,422			327,601
Amortization of acquired sales contracts, net	(3,004		)	(7,975		)	—		3,392			—			(7,587		)
Asset impairment and mine closure costs	—			126,449			—		16,280			78,150			220,879
Total assets	1,897,218			4,141,072			146,947		137,941			3,208,277			9,531,455
Capital expenditures	5,671			137,390			13,147		4,776			62,184			223,168

Nine months ended September 30, 2012
Revenues	$	1,130,408		$	1,409,776		$	272,359	$	88,549		$	—		$	2,901,092
Income (loss) from operations	94,163			(388,563		)	34,937		(3,757		)	(186,634		)	(449,854		)
Depreciation, depletion and amortization	122,298			210,789			29,894		9,704			1,946			374,631
Amortization of acquired sales contracts, net	(1,374		)	(21,658		)	—		471			—			(22,561		)
Asset impairment and mine closure costs	—			524,115			—		(437		)	(239		)	523,439
Total assets	2,234,941			4,130,273			676,057		169,981			2,724,602			9,935,854
Capital expenditures	15,399			222,177			42,761		8,153			15,478			303,968

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

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



	Three Months Ended September 30,						Nine Months Ended September 30,
	2013			2012			2013			2012
	(In thousands)
Income (loss) from operations	$	(234,753	)	$	119,242		$	(322,463	)	$	(449,854	)
Interest expense	(95,624		)	(75,710		)	(285,454		)	(229,210		)
Interest and investment income	697			1,459			4,749			3,568
Other nonoperating expense	$	—		$	—		$	—		$	(19,042	)
Income (loss) from continuing operations before income taxes	$	(329,680	)	$	44,991		$	(603,168	)	$	(694,538	)

Supplemental Condensed Consolidating Financial Information (Tables)

9 Months Ended

Sep. 30, 2013

Supplemental Condensed Consolidating Financial Information [Abstract]

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

Condensed Consolidating Statements of Operations

Three Months Ended September 30, 2013



	Parent/Issuer			Guarantor Subsidiaries			Non- Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Revenues	$	—		$	791,269		$	—		$	—		$	791,269
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	169			688,543			—			—			688,712
Depreciation, depletion and amortization	1,549			104,765			9			—			106,323
Amortization of acquired sales contracts, net	—			(2,568		)	—			—			(2,568		)
Change in fair value of coal derivatives and coal trading activities, net	—			9,753			—			—			9,753
Asset impairment and mine closure costs	57,668			142,729			—			—			200,397
Selling, general and administrative expenses	19,104			8,214			1,482			—			28,800
Other operating income, net	2,345			(7,740		)	—			—			(5,395		)
	80,835			943,696			1,491			—			1,026,022
Loss from investment in subsidiaries	(61,537		)	—			—			61,537			—
Loss from operations	(142,372		)	(152,427		)	(1,491		)	61,537			(234,753		)
Interest expense, net
Interest expense	(114,536		)	(6,222		)	(1,070		)	26,204			(95,624		)
Interest and investment income	6,606			18,975			1,320			(26,204		)	697
	(107,930		)	12,753			250			—			(94,927		)

Loss from continuing operations before income taxes	(250,302		)	(139,674		)	(1,241		)	61,537			(329,680		)
Provision for (benefit from) income taxes	(121,939		)	—			26			—			(121,913		)
Loss from continuing operations	(128,363		)	(139,674		)	(1,267		)	61,537			(207,767		)
Income from discontinued operations, including gain on sale - net of tax	—			79,404			—			—			79,404
Net loss	$	(128,363	)	$	(60,270	)	$	(1,267	)	$	61,537		$	(128,363	)
Total comprehensive loss	$	(125,996	)	$	(59,241	)	$	(1,267	)	$	60,508		$	(125,996	)

Condensed Consolidating Statements of Operations

Nine Months Ended September 30, 2013



	Parent/Issuer			Guarantor Subsidiaries			Non- Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Revenues	$	—		$	2,294,971		$	—		$	—		$	2,294,971
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	4,881			1,989,772			—			—			1,994,653
Depreciation, depletion and amortization	4,430			323,144			27			—			327,601
Amortization of acquired sales contracts, net	—			(7,587		)	—			—			(7,587		)
Change in fair value of coal derivatives and coal trading activities, net	—			2,053			—			—			2,053
Asset impairment and mine closure costs	78,150			142,729			—			—			220,879
Selling, general and administrative expenses	63,006			28,978			4,327			—			96,311
Other operating income, net	(4,663		)	(10,704		)	(1,109		)	—			(16,476		)
	145,804			2,468,385			3,245			—			2,617,434
Loss from investment in subsidiaries	(42,199		)	—			—			42,199			—
Loss from operations	(188,003		)	(173,414		)	(3,245		)	42,199			(322,463		)
Interest expense, net
Interest expense	(336,310		)	(18,502		)	(3,170		)	72,528			(285,454		)
Interest and investment income	22,917			49,986			4,374			(72,528		)	4,749
	(313,393		)	31,484			1,204			—			(280,705		)

Loss from continuing operations before income taxes	(501,396		)	(141,930		)	(2,041		)	42,199			(603,168		)
Provision for (benefit from) income taxes	(230,778		)	—			44			—			(230,734		)
Loss from continuing operations	(270,618		)	(141,930		)	(2,085		)	42,199			(372,434		)
Income from discontinued operations, including gain on sale - net of tax	—			101,816			—			—			101,816
Net loss	$	(270,618	)	$	(40,114	)	$	(2,085	)	$	42,199		$	(270,618	)
Total comprehensive loss	$	(262,717	)	$	(39,175	)	$	(2,085	)	$	41,260		$	(262,717	)

Condensed Consolidating Statements of Operations

Three Months Ended September 30, 2012



	Parent/Issuer			Guarantor Subsidiaries			Non- Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Revenues	$	—		$	975,170		$	—		$	—		$	975,170
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	2,437			806,052			—			—			808,489
Depreciation, depletion and amortization	1,399			117,534			9			—			118,942
Amortization of acquired sales contracts, net	—			(4,093		)	—			—			(4,093		)
Change in fair value of coal derivatives and coal trading activities, net	—			5,840			—			—			5,840
Asset impairment and mine closure costs	—			(2,144		)	—			—			(2,144		)
Legal contingencies	—			(79,532		)	—			—			(79,532		)
Selling, general and administrative expenses	22,051			9,432			1,783			—			33,266
Other operating income, net	(11,052		)	(13,699		)	(89		)	—			(24,840		)
	14,835			839,390			1,703			—			855,928
Income from investment in subsidiaries	164,152			—			—			(164,152		)	—
Income (loss) from operations	149,317			135,780			(1,703		)	(164,152		)	119,242
Interest expense, net
Interest expense	(91,577		)	(6,870		)	(649		)	23,386			(75,710		)
Interest and investment income	8,329			14,570			1,946			(23,386		)	1,459
	(83,248		)	7,700			1,297			—			(74,251		)

Income (loss) from continuing operations before income taxes	66,069			143,480			(406		)	(164,152		)	44,991
Provision for income taxes	20,318			—			—			—			20,318
Income (loss) from continuing operations	45,751			143,480			(406		)	(164,152		)	24,673
Income from discontinued operations, net of tax	—			21,078			—			—			21,078
Net income (loss)	$	45,751		$	164,558		$	(406	)	$	(164,152	)	$	45,751
Total comprehensive income (loss)	$	44,299		$	163,375		$	(406	)	$	(162,969	)	$	44,299

Condensed Consolidating Statements of Operations

Nine Months Ended September 30, 2012



	Parent/Issuer			Guarantor Subsidiaries			Non- Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Revenues	$	—		$	2,901,092		$	—		$	—		$	2,901,092
Costs, expenses and other													—
Cost of sales (exclusive of items shown separately below)	7,694			2,406,612			—			—			2,414,306
Depreciation, depletion and amortization	3,959			370,648			24			—			374,631
Amortization of acquired sales contracts, net	—			(22,561		)	—			—			(22,561		)
Change in fair value of coal derivatives and coal trading activities, net	—			(29,827		)	—			—			(29,827		)
Asset impairment and mine closure costs	—			523,439			—			—			523,439
Goodwill impairment	—			115,791			—			—			115,791
Legal contingencies	—			(79,532		)	—			—			(79,532		)
Selling, general and administrative expenses	62,469			30,965			5,871			—			99,305
Other operating income, net	(7,693		)	(23,811		)	(13,102		)	—			(44,606		)
	66,429			3,291,724			(7,207		)	—			3,350,946
Loss from investment in subsidiaries	(324,429		)	—			—			324,429			—
Income (loss) from operations	(390,858		)	(390,632		)	7,207			324,429			(449,854		)
Interest expense, net
Interest expense	(263,381		)	(27,285		)	(2,382		)	63,838			(229,210		)
Interest and investment income	19,087			42,508			5,811			(63,838		)	3,568
	(244,294		)	15,223			3,429			—			(225,642		)
Other non-operating expense
Net loss resulting from early retirement of ICG debt	(17,349		)	(1,693		)	—			—			(19,042		)

Income (loss) from continuing operations before income taxes	(652,501		)	(377,102		)	10,636			324,429			(694,538		)
Provision for (benefit from) income taxes	(264,237		)	—			1,581			—			(262,656		)
Income (loss) from continuing operations	(388,264		)	(377,102		)	9,055			324,429			(431,882		)
Income from discontinued operations, net of tax	—			43,618			—			—			43,618
Net Income (loss)	(388,264		)	(333,484		)	9,055			324,429			(388,264		)
Less: Net income attributable to noncontrolling interest	(268		)	—			—			—			(268		)
Net Income (loss) attributable to Arch Coal, Inc.	$	(388,532	)	$	(333,484	)	$	9,055		$	324,429		$	(388,532	)
Total comprehensive income (loss)	$	(385,523	)	$	(336,648	)	$	9,055		$	327,593		$	(385,523	)

Schedule of Condensed Consolidating Balance Sheets [Table Text Block]

Condensed Consolidating Balance Sheets

September 30, 2013



	Parent/Issuer		Guarantor Subsidiaries		Non-Guarantor Subsidiaries		Eliminations			Consolidated
	(In thousands)
Assets
Cash and cash equivalents	$	1,021,245	$	100,410	$	11,473	$	—		$	1,133,128
Restricted cash	—		—		—		—			—
Short term investments	248,724		—		—		—			248,724
Receivables	7,847		21,178		190,493		(4,679		)	214,839
Inventories	—		287,409		—		—			287,409
Other	96,992		48,270		277		—			145,539
Total current assets	1,374,808		457,267		202,243		(4,679		)	2,029,639

Property, plant and equipment, net	25,526		6,752,687		46		(34		)	6,778,225

Investment in subsidiaries	7,992,601		—		—		(7,992,601		)	—
Intercompany receivables	—		1,986,992		—		(1,986,992		)	—
Note receivable from Arch Western	675,000		—		—		(675,000		)	—
Other	147,950		575,551		90		—			723,591
Total other assets	8,815,551		2,562,543		90		(10,654,593		)	723,591
Total assets	$	10,215,885	$	9,772,497	$	202,379	$	(10,659,306	)	$	9,531,455

Liabilities and Stockholders’ Equity
Accounts payable	$	20,728	$	186,468	$	77	$	—		$	207,273
Accrued expenses and other current liabilities	107,756		246,063		314		(4,679		)	349,454
Current maturities of debt	19,343		3,707		—		—			23,050
Total current liabilities	147,827		436,238		391		(4,679		)	579,777
Long-term debt	5,055,021		19,363		—		—			5,074,384
Intercompany payables	1,810,718		—		176,274		(1,986,992		)	—
Note payable to Arch Coal	—		675,000		—		(675,000		)	—
Asset retirement obligations	1,150		409,971		—		—			411,121
Accrued pension benefits	36,304		32,235		—		—			68,539
Accrued postretirement benefits other than pension	14,267		30,012		—		—			44,279
Accrued workers’ compensation	25,601		56,413		—		—			82,014
Deferred income taxes	484,130		—		—		—			484,130
Other noncurrent liabilities	59,179		146,055		323		—			205,557
Total liabilities	7,634,197		1,805,287		176,988		(2,666,671		)	6,949,801
Stockholders’ equity	2,581,688		7,967,210		25,391		(7,992,635		)	2,581,654
Total liabilities and stockholders’ equity	$	10,215,885	$	9,772,497	$	202,379	$	(10,659,306	)	$	9,531,455

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	—		1,600,311		—		(1,600,311		)	—
Note receivable from Arch Western	675,000		—		—		(675,000		)	—
Other	187,171		568,314		90		—			755,575
Total other assets	9,116,679		2,168,625		90		(10,529,819		)	755,575
Total assets	$	10,209,293	$	10,071,396	$	260,731	$	(10,534,643	)	$	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	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
Intercompany payables	1,367,739		—		232,572		(1,600,311		)	—
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	7,354,726		1,844,360		233,259		(2,280,135		)	7,152,210
Stockholders’ equity	2,854,567		8,227,036		27,472		(8,254,508		)	2,854,567
Total liabilities and stockholders’ equity	$	10,209,293	$	10,071,396	$	260,731	$	(10,534,643	)	$	10,006,777

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

Condensed Consolidating Statements of Cash Flows

Nine Months Ended September 30, 2013



	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$	(22,206	)	$	153,868		$	54,930		$	—		$	186,592
Investing Activities
Capital expenditures	(2,488		)	(220,680		)	—			—			(223,168		)
Minimum royalty payments	—			(10,901		)	—			—			(10,901		)
Proceeds from dispositions of property, plant and equipment	—			8,799			—			—			8,799
Proceeds from sales-leaseback transactions	—			34,919			—			—			34,919
Proceeds from sale of Canyon Fuel	—			422,663			—			—			422,663
Purchases of short term investments	(85,418		)	—			—			—			(85,418		)
Proceeds from sales of short term investments	67,255			—			—			—			67,255
Investments in and advances to affiliates	(4,016		)	(7,492		)	—			384			(11,124		)
Change in restricted cash	3,453			—			—			—			3,453
Cash provided by (used in) investing activities	(21,214		)	227,308			—			384			206,478
Financing Activities
Contributions from parent	—			384			—			(384		)	—
Payments on term loan	(12,375		)	—			—			—			(12,375		)
Payments to retire debt	—			(384		)	—			—			(384		)
Net payments on other debt	(12,700		)	—			—			—			(12,700		)
Dividends paid	(19,105		)	—			—			—			(19,105		)
Transactions with affiliates, net	437,532			(381,234		)	(56,298		)	—			—
Cash provided by (used in) financing activities	393,352			(381,234		)	(56,298		)	(384		)	(44,564		)
Increase (decrease) in cash and cash equivalents	349,932			(58		)	(1,368		)	—			348,506
Cash and cash equivalents, beginning of period	671,313			100,468			12,841			—			784,622
Cash and cash equivalents, end of period	$	1,021,245		$	100,410		$	11,473		$	—		$	1,133,128

Condensed Consolidating Statements of Cash Flows

Nine Months Ended September 30, 2012



	Parent/Issuer			Guarantor Subsidiaries			Non-Guarantor Subsidiaries			Eliminations			Consolidated
	(In thousands)
Cash provided by (used in) operating activities	$	(610,129	)	$	874,545		$	91,979		$	—		$	356,395
Investing Activities
Capital expenditures	(4,150		)	(299,818		)	—			—			(303,968		)
Minimum royalty payments	—			(9,192		)	—			—			(9,192		)
Proceeds from dispositions of property, plant and equipment	—			1,127			21,497			—			22,624
Purchases of short term investments	(99,628		)	—			—			—			(99,628		)
Investments in and advances to affiliates	(5,138		)	(9,082		)	—			1,535			(12,685		)
Purchase of noncontrolling interest	—			(17,500		)	—			—			(17,500		)
Change in restricted cash	6,872			—			—			—			6,872
Cash provided by (used in) investing activities	(102,044		)	(334,465		)	21,497			1,535			(413,477		)
Financing Activities
Contributions from parent	—			1,535			—			(1,535		)	—
Proceeds from issuance of term loan	1,386,000			—			—			—			1,386,000
Payments on term loan	(3,500		)	—			—			—			(3,500		)
Payments to retire debt	—			(452,806		)	—			—			(452,806		)
Net decrease in borrowings under lines of credit	(375,000		)	—			(6,300		)	—			(381,300		)
Net payments from other debt	(13,078		)	—			—			—			(13,078		)
Debt financing costs	(34,640		)	—			(46		)	—			(34,686		)
Dividends paid	(36,072		)	—			—			—			(36,072		)
Proceeds from exercise of options under incentive plans	5,131			—			—			—			5,131
Transactions with affiliates, net	30,338			66,364			(96,702		)	—			—
Cash provided by (used in) financing activities	959,179			(384,907		)	(103,048		)	(1,535		)	469,689
Increase in cash and cash equivalents	247,006			155,173			10,428			—			412,607
Cash and cash equivalents, beginning of period	66,542			70,258			1,349			—			138,149
Cash and cash equivalents, end of period	$	313,548		$	225,431		$	11,777		$	—		$	550,756

Basis of Presentation (Narrative) (Details)	9 Months Ended
Basis of Presentation (Narrative) (Details)	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
number of mining complexes temporarily idled	1
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of mining complexes operated	3
Long-Lived Assets to be Abandoned, Asset Name [Domain]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of mining complexes operated	4

Discontinued Operations (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Discontinued Operations and Disposal Groups [Abstract]
Proceeds from sale of Canyon Fuel	$ 422,663

Discontinued Operations (Schedule of Results of Discontinued Operations) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Discontinued Operations and Disposal Groups [Abstract]
Total Revenues	$ 45,763	$ 112,448	$ 219,002	$ 289,715
Income from discontinued operations before income taxes	3,429	16,718	32,166	50,911
Gain on sale	115,679		115,679
Income tax expense (benefit)	39,704	(4,360)	46,029	7,293
Income from discontinued operations, including gain on sale - net of tax	$ 79,404	$ 21,078	$ 101,816	$ 43,618
Basic earnings per common share from discontinued operations	$ 0.37	$ 0.10	$ 0.48	$ 0.21
Diluted earnings per common share from discontinued operations	$ 0.37	$ 0.10	$ 0.48	$ 0.21

Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2013 USD ($)
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	$ (16,507)
Unrealized gains	7,788
Amounts reclassified from accumulated other comprehensive income	113
Balance at September 30, 2013	(8,606)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	2,244
Unrealized gains	1,197
Amounts reclassified from accumulated other comprehensive income	(1,339)
Balance at September 30, 2013	2,102
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	(18,286)
Unrealized gains	1,938
Amounts reclassified from accumulated other comprehensive income	1,252
Balance at September 30, 2013	(15,096)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	(465)
Unrealized gains	4,653
Amounts reclassified from accumulated other comprehensive income	200
Balance at September 30, 2013	$ 4,388

- Definition

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

+ References + Details

Accumulated Other Comprehensive Income (Loss) (Schedule of Reclassifications) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Revenues	$ 791,269	$ 975,170	$ 2,294,971	$ 2,901,092
Loss from continuing operations before income taxes	(329,680)	44,991	(603,168)	(694,538)
Provision for (benefit from) income taxes	121,913	(20,318)	230,734	262,656
Net income (loss)	(128,363)	$ 45,751	(270,618)	$ (388,264)
reclassification out of accumulated other comprehensive income [Member] \| Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of prior service credits	5,573		11,154
Amortization of actuarial gains (losses), net	(3,823)		(13,108)
Loss from continuing operations before income taxes	1,750		(1,954)
Provision for (benefit from) income taxes	(631)		702
Net income (loss)	1,119		(1,252)
reclassification out of accumulated other comprehensive income [Member] \| Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and investment income	(4)		(313)
Provision for (benefit from) income taxes	2		113
Net income (loss)	(2)		(200)
Commodity Contract [Member] \| reclassification out of accumulated other comprehensive income [Member] \| Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Revenues	692		2,093
Provision for (benefit from) income taxes	(249)		(754)
Net income (loss)	$ 443		$ 1,339

Impairment Charges Impairment Charges (Details) - Impaired Long-Lived Assets Held and Used, Asset Name [Domain] $ in Millions	9 Months Ended
	Sep. 30, 2013 USD ($)
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment and mine closure costs	$ 142.8
Assets, Fair Value Disclosure, Nonrecurring	$ 71.3

Inventories (Inventories) (Details) - USD ($) $ in Thousands	Sep. 30, 2013	Dec. 31, 2012
Inventory Disclosure [Abstract]
Coal	$ 134,481	$ 180,917
Repair parts and supplies	143,763	172,139
Work-in-process	9,165	12,368
Inventories	287,409	365,424
Allowance for slow-moving and obsolete inventories	$ 8,800	$ 13,600

Investments in Available-for-Sale Securities (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	$ 254,559	$ 240,382
Gross Unrealized Gains	10,312	2,706
Gross Unrealized Losses	(3,457)	(3,436)
Fair Value	261,414	239,652
Total Investments	248,724	234,305
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	123,809	146,993
Available-for-sale Debt Securities Gross Unrealized Gain	7	2
Available-for-sale Debt Securities, Gross Unrealized Loss	(126)	(412)
Fair Value	123,690	146,583
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	125,479	88,118
Available-for-sale Debt Securities Gross Unrealized Gain	21
Available-for-sale Debt Securities, Gross Unrealized Loss	(466)	(396)
Fair Value	125,034	87,722
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost Basis	5,271	5,271
Available-for-sale Equity Securities, Gross Unrealized Gain	10,284	2,704
Available-for-sale Equity Securities, Gross Unrealized Loss	(2,865)	(2,628)
Fair Value	12,690	5,347
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
U.S. government and agency securities	123,690	146,583
Corporate notes and bonds	125,034	87,722
Total Investments	248,724	234,305
Other Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Equity securities	$ 12,690	$ 5,347

Investments in Available-for-Sale Securities (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2013	Dec. 31, 2012
Available-for-sale Securities [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 167.5	$ 223.3
Available-for-sale Securities, Continuous Unrealized Loss Position, Greater than Twelve Months, Fair Value	$ 51.6	$ 0.4

Equity Investments And Membership Interests In Joint Ventures (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Schedule of Equity Method Investments [Line Items]
Equity method investment impairment	$ 200,397		$ (2,144)	$ 220,879	$ 523,439
Impairment of equity investment				(28,947)
Tenaska [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment impairment		$ 20,500
Impairment of equity investment		(15,264)
Note Receivable from Equity Method Investee, Write-downs		$ 5,200
Equity Method Investment, Ownership Percentage		35.00%
DKRW [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment impairment				57,700
Impairment of equity investment				(13,683)
Note Receivable from Equity Method Investee, Write-downs				$ 44,000
Equity Method Investment, Ownership Percentage	24.00%			24.00%
Equity Method Investee [Member]
Schedule of Equity Method Investments [Line Items]
Future development costs, maximum limit	$ 58,500			$ 58,500

Equity Investments And Membership Interests In Joint Ventures (Schedule Of Equity Method Investments) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Jun. 30, 2013	Sep. 30, 2013
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at December 31, 2012		$ 242,215
Advances to (distributions from) affiliates, net		4,845
Equity in comprehensive income (loss)		(5,441)
Impairment of equity investment		(28,947)
Balance at September 30, 2013		223,554
Knight Hawk [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at December 31, 2012		149,063
Advances to (distributions from) affiliates, net		(5,342)
Equity in comprehensive income (loss)		(13,362)
Impairment of equity investment
Balance at September 30, 2013		157,083
DKRW [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at December 31, 2012		15,515
Advances to (distributions from) affiliates, net
Equity in comprehensive income (loss)		1,832
Impairment of equity investment		(13,683)
Balance at September 30, 2013
DTA [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at December 31, 2012		15,462
Advances to (distributions from) affiliates, net		2,537
Equity in comprehensive income (loss)		3,855
Impairment of equity investment
Balance at September 30, 2013		14,144
Tenaska [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at December 31, 2012		15,264
Advances to (distributions from) affiliates, net
Equity in comprehensive income (loss)
Impairment of equity investment	$ (15,264)
Balance at September 30, 2013
Millennium [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at December 31, 2012		32,214
Advances to (distributions from) affiliates, net		4,954
Equity in comprehensive income (loss)		1,953
Impairment of equity investment
Balance at September 30, 2013		35,215
Tongue River [Member]
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Balance at December 31, 2012		14,697
Advances to (distributions from) affiliates, net		2,696
Equity in comprehensive income (loss)		281
Impairment of equity investment
Balance at September 30, 2013		$ 17,112

Derivatives (Narrative) (Details) $ in Thousands, gal in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2013 USD ($)	Sep. 30, 2012 USD ($)	Sep. 30, 2013 USD ($) gal	Sep. 30, 2012 USD ($)	Dec. 31, 2012 USD ($)
Derivative [Line Items]
Current asset (liability) for the right to reclaim cash collateral	$ (4,900)		$ (4,900)		$ 16,200
Net unrealized and realized gains (losses) related to trading portfolio	900	$ 5,500	3,000	$ 6,200
Gain on derivative contracts designated as hedge instruments in cash flow hedges to be reclassified from OCI into earnings during the next twelve months	2,900		2,900
Net derivative assets as classified in the balance sheet	$ 27,061		27,061		$ 32,315
Year One [Member]
Derivative [Line Items]
Value of trading portfolio realized			400
Year Two [Member]
Derivative [Line Items]
Value of trading portfolio realized			$ 7,000
Diesel Purchases [Member] \| Year One [Member]
Derivative [Line Items]
Percent of expected requirements covered	94.00%		94.00%
Diesel Purchases [Member] \| Year Two [Member]
Derivative [Line Items]
Percent of expected requirements covered	82.00%		82.00%
Diesel Purchases [Member] \| Heating Oil [Member]
Derivative [Line Items]
Quantities under derivative contracts	65,000,000		65,000,000
Diesel Purchases [Member] \| Minimum Annual Purchase [Member]
Derivative [Line Items]
Gallons of diesel fuel purchased annually \| gal			57
Diesel Purchases [Member] \| Maximum [Member]
Derivative [Line Items]
Gallons of diesel fuel purchased annually \| gal			67
Diesel Usage Fuel Surcharges [Member] \| Heating Oil [Member] \| Year One [Member]
Derivative [Line Items]
Quantities under derivative contracts	2,800,000		2,800,000
Diesel Usage Fuel Surcharges [Member] \| Heating Oil [Member] \| Year Two [Member]
Derivative [Line Items]
Quantities under derivative contracts	4,000,000		4,000,000

Derivatives (Schedule of Price Risk Derivatives) (Details) number in Thousands	Sep. 30, 2013
Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	7,552
Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held	1,869
Year One [Member] \| Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	2,314
Year One [Member] \| Coal Purchases [Member]
Derivative [Line Items]
Derivatives Held	609
Year Two [Member] \| Coal Sales [Member]
Derivative [Line Items]
Derivatives Held	4,458
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

Derivatives (Disclosure Of Fair Value Of Derivatives) (Details) - USD ($) $ in Thousands	Sep. 30, 2013	Dec. 31, 2012
Derivative [Line Items]
Derivative Assets	$ 82,930	$ 54,863
Derivative Liabilities	(56,290)	(24,285)
Effect of counterparty netting in derivative assets	(55,869)	(22,548)
Effect of counterparty netting in derivative liabilities	55,869	22,548
Net derivative assets as classified in the balance sheet	27,061	32,315
Net derivative liabilities as classified in the balance sheet	(421)	(1,737)
Net derivatives as classified in the balance sheet	26,640	30,578
Designated as Hedging Instrument [Member] \| Coal [Member]
Derivative [Line Items]
Derivative Assets	3,009	3,277
Derivative Liabilities	(4)	(10)
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Assets	79,921	51,586
Derivative Liabilities	(56,286)	(24,275)
Not Designated as Hedging Instrument [Member] \| Coal [Member]
Derivative [Line Items]
Derivative Assets	15,907	24,843
Derivative Liabilities	(3,903)	(7,342)
Not Designated as Hedging Instrument [Member] \| Coal Held for Trading Purposes [Member]
Derivative [Line Items]
Derivative Assets	59,789	17,403
Derivative Liabilities	(52,383)	(16,933)
Not Designated as Hedging Instrument [Member] \| Heating Oil-Diesel Purchases [Member]
Derivative [Line Items]
Derivative Assets	3,825	7,379
Derivative Liabilities
Not Designated as Hedging Instrument [Member] \| Heating Oil-Fuel Surchages [Member]
Derivative [Line Items]
Derivative Assets	400	1,961
Derivative Liabilities

Derivatives (Net Derivatives As Reflected On The Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ 26,640	$ 30,578
Other Current Assets [Member] \| Heating Oil [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	4,225	9,340
Coal Derivative Assets [Member] \| Coal [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	22,836	22,975
Coal Derivative Liabilities [Member] \| Coal [Member]
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ (421)	$ (1,737)

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

3 Months Ended

9 Months Ended

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Derivative Instruments, Gain (Loss) [Line Items]

Gain (Loss) Recognized in OCI (Effective Portion)

$ 2,190

$ 81

$ 1,797

^[1]

$ 3,861

^[1]

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

788

542

2,189

^[1]

1,552

^[1]

Coal Purchases [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Gain (Loss) Recognized in OCI (Effective Portion)

(942)

(178)

(511)

^[1]

(1,122)

^[1]

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

(123)

(633)

^[1]

Coal Sales [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Gain (Loss) Recognized in OCI (Effective Portion)

3,132

259

2,308

^[2]

4,983

^[2]

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

911

542

2,822

^[2]

1,552

^[2]

Coal [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Unrealized Gain (Loss) on Derivatives

(10,668)

(11,328)

(5,089)

^[3]

23,670

^[3]

Coal derivative settlements, non-hedging

9,929

14,072

25,725

^[4]

25,901

^[4]

Heating Oil-Diesel Purchases [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Realized Gains (Losses)

(288)

5,184

(9,760)

^[4]

(16,902)

^[4]

Heating Oil-Fuel Surchages [Member]

Derivative Instruments, Gain (Loss) [Line Items]

Realized Gains (Losses)

$ (222)

$ 1,092

$ (817)

^[4]

$ (1,140)

^[4]

[1]	Cost of sales
[2]	Revenues
[3]	Change in fair value of coal derivatives and coal trading activities, net
[4]	Other operating income, net

Debt (Debt) (Details) - USD ($) $ in Thousands	9 Months Ended
Debt (Debt) (Details) - USD ($) $ in Thousands	Sep. 30, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Other	$ 25,912	$ 40,350
Total	5,097,434	5,118,775
Current maturities of debt	23,050	32,896
Long-term debt	5,074,384	5,085,879
Available borrowing capacity under lines of credit	204,000
Loans Payable [Member]
Debt Instrument [Line Items]
Term loan ($1.63 billion face value) due 2018	$ 1,617,097	1,627,384
Debt Instrument, Basis Spread on Variable Rate	4.50%
Debt Instrument, Face Amount	$ 1,630,000
8.75% Senior Notes Due 2016 [Member]
Debt Instrument [Line Items]
Senior notes	$ 592,646	590,999
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	$ 361,779	360,042
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%

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012
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	$ 4,500.0	$ 4,500.0	$ 5,000.0
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net unrealized losses related to level 3 financial instruments	$ 0.2	$ 4.8

Fair Value Measurements (Summary Of Change In The Fair Values Of Financial Instruments Categorized As Level 3) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 3,438	$ 8,174
Realized and unrealized losses recognized in earnings, net	(570)	(9,882)
Purchases	1,464	7,317
Issuances		(25)
Settlements	(238)	(1,490)
Ending balance	$ 4,094	$ 4,094

Fair Value Measurements (Summary Of Financial Assets And Liabilities Accounted For At Fair Value) (Details) - USD ($) $ in Thousands	Sep. 30, 2013	Dec. 31, 2012
Assets:
Investments in marketable securities	$ 261,414	$ 239,652
Derivatives	27,061	32,315
Total assets	288,475
Liabilities:
Coal derivative liabilities	421	$ 1,737
Level 1 [Member]
Assets:
Investments in marketable securities	101,338
Derivatives	22,750
Total assets	124,088
Liabilities:
Coal derivative liabilities
Level 2 [Member]
Assets:
Investments in marketable securities	160,076
Derivatives
Total assets	160,076
Liabilities:
Coal derivative liabilities	204
Level 3 [Member]
Assets:
Investments in marketable securities
Derivatives	4,311
Total assets	4,311
Liabilities:
Coal derivative liabilities	$ 217

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2013	Dec. 31, 2012
Accrued Expenses and Other Current Liabilities [Abstract]
Payroll and employee benefits	$ 68,245	$ 72,405
Taxes other than income taxes	113,872	121,029
Interest	80,454	42,413
Acquired sales contracts	14,461	14,038
Workers’ compensation	12,215	10,371
Asset retirement obligations	38,895	38,920
Other	20,891	18,842
Accrued Liabilities, Current	$ 349,033	$ 318,018

Stock-Based Compensation And Other Incentive Plans (Narrative) (Details) - USD ($)	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Common Shares	2,000,000
Weighted average exercise price of options granted	$ 5.23
Options granted, weighted average grant date fair value	$ 2.37
Option, weighted average risk free rate	0.65%
Option, weighted average dividend yield	2.30%
Option, weighted average volatility	66.74%
Amounts unpaid under long term incentive plan	$ 15,000,000	$ 13,100,000
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life of options	4 years 6 months
Share based awards vesting period	3 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based awards vesting period	3 years
Stock Issued During Period, Shares, Restricted Stock Award, Gross	969,100
Stock Issued During Period, Value, Restricted Stock Award, Gross	$ 5.20

Workers' Compensation (Worker's Compensation Expense) (Details) - Workers' Compensation [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accrued Workers' Compensation [Line Items]
Service cost	$ 363	$ 419	$ 1,373	$ 1,458
Interest cost	709	629	2,022	1,708
Net amortization	262		731	(574)
Curtailments	816		816	1,933
Total net benefit	2,150	1,048	4,942	4,525
Traumatic injury claims and assessments	4,114	7,453	16,263	19,052
Total workers’ compensation expense	$ 6,264	$ 8,501	$ 21,205	$ 23,577

Employee Benefit Plans (Pension And Other Postretirement Benefit Costs) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 6,672	$ 6,156	$ 21,162	$ 21,062
Interest cost	3,994	3,683	11,796	11,755
Curtailments	47		47	324
Expected return on plan assets	(5,848)	(5,508)	(17,690)	(16,523)
Amortization of prior service cost (credit)	(51)	273	(152)	200
Amortization of other actuarial (gains) losses	3,617	3,248	12,430	11,019
Total net benefit	8,431	7,852	27,593	27,837
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	497	541	1,591	1,629
Interest cost	427	508	1,273	1,519
Curtailments	(5,444)	(2,212)	(5,444)	(4,049)
Amortization of prior service cost (credit)	(2,641)	(2,837)	(8,121)	(8,708)
Amortization of other actuarial (gains) losses	(55)	(130)	(53)	(391)
Total net benefit	$ (7,216)	$ (4,130)	$ (10,754)	$ (10,000)

Earnings Per Common Share (Narrative) (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]
Effect of options to purchase common stock	7.0	5.8	7.9	5.0

Settlement with Patriot Coal (Details) $ in Millions	9 Months Ended
Settlement with Patriot Coal (Details) $ in Millions	Sep. 30, 2013 USD ($)
Subsequent Event [Line Items]
Payments for Legal Settlements	$ 15.6
Purchase commitment, remaining minimum amount committed	16.0
Letters of credit posted in the Companys favor	16.7
Subsequent Event [Member]
Subsequent Event [Line Items]
Payments for Legal Settlements	$ 5.0

Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Aug. 25, 2011	Aug. 13, 2007
Purchase replacement coal				$ 100.0
Damages and interest awarded			$ 104.1
Payments for Legal Settlements	$ 15.6
Amount accrued	21.2	$ 32.8
Amount accrued current portion	7.7	$ 4.4
Maximum [Member]
Aggregate amount of past and future damages	377.0
Minimum [Member]
Aggregate amount of past and future damages	$ 228.0
past damages [Member]
Damages and interest awarded			13.8
future damages [Member]
Damages and interest awarded			$ 90.3

Segment Information (Narrative) (Details)	9 Months Ended
Segment Information (Narrative) (Details)	Sep. 30, 2013
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		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Revenues	$ 791,269	$ 975,170	$ 2,294,971	$ 2,901,092
Income (loss) from operations	(234,753)	119,242	(322,463)	(449,854)
Depreciation, depletion and amortization	106,323	118,942	327,601	374,631
Amortization of acquired sales contracts, net	(2,568)	(4,093)	(7,587)	(22,561)
Asset impairment and mine closure costs	200,397	(2,144)	220,879	523,439
Total assets	9,531,455	9,935,854	9,531,455	9,935,854	$ 10,006,777
Capital expenditures	54,104	101,895	223,168	303,968
PRB [Member]
Segment Reporting Information [Line Items]
Revenues	420,521	406,719	1,135,892	1,130,408
Income (loss) from operations	20,694	38,873	53,244	94,163
Depreciation, depletion and amortization	46,619	43,944	130,993	122,298
Amortization of acquired sales contracts, net	(864)	(589)	(3,004)	(1,374)
Asset impairment and mine closure costs
Total assets	1,897,218	2,234,941	1,897,218	2,234,941
Capital expenditures	1,695	5,620	5,671	15,399
APP [Member]
Segment Reporting Information [Line Items]
Revenues	263,188	436,409	883,484	1,409,776
Income (loss) from operations	(157,883)	88,695	(190,278)	(388,563)
Depreciation, depletion and amortization	46,529	61,596	157,866	210,789
Amortization of acquired sales contracts, net	(2,691)	(3,711)	(7,975)	(21,658)
Asset impairment and mine closure costs	126,449	(1,801)	126,449	524,115
Total assets	4,141,072	4,130,273	4,141,072	4,130,273
Capital expenditures	44,624	77,772	137,390	222,177
WBIT [Member]
Segment Reporting Information [Line Items]
Revenues	78,022	105,515	187,374	272,359
Income (loss) from operations	9,287	24,110	23,766	34,937
Depreciation, depletion and amortization	9,436	9,985	26,528	29,894
Amortization of acquired sales contracts, net
Asset impairment and mine closure costs
Total assets	146,947	676,057	146,947	676,057
Capital expenditures	5,859	13,510	13,147	42,761
Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	29,538	26,527	88,221	88,549
Income (loss) from operations	(9,231)	(1,298)	(407)	(3,757)
Depreciation, depletion and amortization	2,523	2,594	7,792	9,704
Amortization of acquired sales contracts, net	987	207	3,392	471
Asset impairment and mine closure costs	16,280	(210)	16,280	(437)
Total assets	137,941	169,981	137,941	169,981
Capital expenditures	1,263	3,640	4,776	8,153
Corporate, Other and Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues
Income (loss) from operations	(97,620)	(31,138)	(208,788)	(186,634)
Depreciation, depletion and amortization	1,216	823	4,422	1,946
Amortization of acquired sales contracts, net
Asset impairment and mine closure costs	57,668	(133)	78,150	(239)
Total assets	3,208,277	2,724,602	3,208,277	2,724,602
Capital expenditures	$ 663	$ 1,353	$ 62,184	$ 15,478

Segment Information (Reconciliation Statement Of Segment Income from Operations To Consolidated Income Before Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting [Abstract]
Income (loss) from operations	$ (234,753)	$ 119,242	$ (322,463)	$ (449,854)
Interest expense	(95,624)	(75,710)	(285,454)	(229,210)
Interest and investment income	697	1,459	4,749	3,568
Other nonoperating expenses				(19,042)
Income (loss) from continuing operations before income taxes	$ (329,680)	$ 44,991	$ (603,168)	$ (694,538)

Supplemental Condensed Consolidating Financial Information (Schedule Of Condensed Consolidating Statements Of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Condensed Financial Statement Line Items
Revenues	$ 791,269	$ 975,170	$ 2,294,971	$ 2,901,092
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	688,712	808,489	1,994,653	2,414,306
Depreciation, depletion and amortization	106,323	118,942	327,601	374,631
Amortization of acquired sales contracts, net	(2,568)	(4,093)	(7,587)	(22,561)
Change in fair value of coal derivatives and coal trading activities, net	9,753	5,840	2,053	(29,827)
Asset impairment and mine closure costs	200,397	(2,144)	220,879	523,439
Legal contingencies		(79,532)		(79,532)
Goodwill impairment				115,791
Selling, general and administrative expenses	28,800	33,266	96,311	99,305
Other operating income, net	(5,395)	(24,840)	(16,476)	(44,606)
Operating Expenses	1,026,022	855,928	2,617,434	3,350,946
Loss from investment in subsidiaries
Income (loss) from operations	(234,753)	119,242	(322,463)	(449,854)
Interest expense, net
Interest expense	(95,624)	(75,710)	(285,454)	(229,210)
Interest and investment income	697	1,459	4,749	3,568
Interest expense, net	(94,927)	(74,251)	(280,705)	(225,642)
Other Nonoperating Income (Expense) [Abstract]
Net loss resulting from early retirement and refinancing of debt				(19,042)
Income (loss) before income taxes	(329,680)	44,991	(603,168)	(694,538)
Provision for (benefit from) income taxes	(121,913)	20,318	(230,734)	(262,656)
Income (Loss) from Continuing Operations	(207,767)	24,673	(372,434)	(431,882)
Income from discontinued operations, including gain on sale - net of tax	79,404	21,078	101,816	43,618
Net income (loss)	(128,363)	45,751	(270,618)	(388,264)
Less: Net income attributable to noncontrolling interest				(268)
Net income (loss) attributable to Arch Coal, Inc.	(128,363)	45,751	(270,618)	(388,532)
Total comprehensive income (loss)	(125,996)	44,299	(262,717)	(385,523)
Parent/Issuer [Member]
Condensed Financial Statement Line Items
Revenues
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	169	2,437	4,881	7,694
Depreciation, depletion and amortization	1,549	1,399	4,430	3,959
Amortization of acquired sales contracts, net
Change in fair value of coal derivatives and coal trading activities, net
Asset impairment and mine closure costs	57,668		78,150
Legal contingencies
Goodwill impairment
Selling, general and administrative expenses	19,104	22,051	63,006	62,469
Other operating income, net	2,345	(11,052)	(4,663)	(7,693)
Operating Expenses	80,835	14,835	145,804	66,429
Loss from investment in subsidiaries	(61,537)	164,152	(42,199)	(324,429)
Income (loss) from operations	(142,372)	149,317	(188,003)	(390,858)
Interest expense, net
Interest expense	(114,536)	(91,577)	(336,310)	(263,381)
Interest and investment income	6,606	8,329	22,917	19,087
Interest expense, net	(107,930)	(83,248)	(313,393)	(244,294)
Other Nonoperating Income (Expense) [Abstract]
Net loss resulting from early retirement and refinancing of debt				(17,349)
Income (loss) before income taxes	(250,302)	66,069	(501,396)	(652,501)
Provision for (benefit from) income taxes	(121,939)	20,318	(230,778)	(264,237)
Income (Loss) from Continuing Operations	(128,363)	45,751	(270,618)	(388,264)
Income from discontinued operations, including gain on sale - net of tax
Net income (loss)				(388,264)
Less: Net income attributable to noncontrolling interest				(268)
Net income (loss) attributable to Arch Coal, Inc.	(128,363)	45,751	(270,618)	(388,532)
Total comprehensive income (loss)	(125,996)	44,299	(262,717)	(385,523)
Guarantor Subsidiaries [Member]
Condensed Financial Statement Line Items
Revenues	791,269	975,170	2,294,971	2,901,092
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)	688,543	806,052	1,989,772	2,406,612
Depreciation, depletion and amortization	104,765	117,534	323,144	370,648
Amortization of acquired sales contracts, net	(2,568)	(4,093)	(7,587)	(22,561)
Change in fair value of coal derivatives and coal trading activities, net	9,753	5,840	2,053	(29,827)
Asset impairment and mine closure costs	142,729	(2,144)	142,729	523,439
Legal contingencies		(79,532)		(79,532)
Goodwill impairment				115,791
Selling, general and administrative expenses	8,214	9,432	28,978	30,965
Other operating income, net	(7,740)	(13,699)	(10,704)	(23,811)
Operating Expenses	943,696	839,390	2,468,385	3,291,724
Loss from investment in subsidiaries
Income (loss) from operations	(152,427)	135,780	(173,414)	(390,632)
Interest expense, net
Interest expense	(6,222)	(6,870)	(18,502)	(27,285)
Interest and investment income	18,975	14,570	49,986	42,508
Interest expense, net	12,753	7,700	31,484	15,223
Other Nonoperating Income (Expense) [Abstract]
Net loss resulting from early retirement and refinancing of debt				(1,693)
Income (loss) before income taxes	(139,674)	143,480	(141,930)	(377,102)
Provision for (benefit from) income taxes
Income (Loss) from Continuing Operations	(139,674)	143,480	(141,930)	(377,102)
Income from discontinued operations, including gain on sale - net of tax	79,404	21,078	101,816	43,618
Net income (loss)				(333,484)
Less: Net income attributable to noncontrolling interest
Net income (loss) attributable to Arch Coal, Inc.	(60,270)	164,558	(40,114)	(333,484)
Total comprehensive income (loss)	(59,241)	163,375	(39,175)	(336,648)
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statement Line Items
Revenues
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)
Depreciation, depletion and amortization	9	9	27	24
Amortization of acquired sales contracts, net
Change in fair value of coal derivatives and coal trading activities, net
Asset impairment and mine closure costs
Legal contingencies
Goodwill impairment
Selling, general and administrative expenses	1,482	1,783	4,327	5,871
Other operating income, net		(89)	(1,109)	(13,102)
Operating Expenses	1,491	1,703	3,245	(7,207)
Loss from investment in subsidiaries
Income (loss) from operations	(1,491)	(1,703)	(3,245)	7,207
Interest expense, net
Interest expense	(1,070)	(649)	(3,170)	(2,382)
Interest and investment income	1,320	1,946	4,374	5,811
Interest expense, net	250	1,297	1,204	3,429
Other Nonoperating Income (Expense) [Abstract]
Net loss resulting from early retirement and refinancing of debt
Income (loss) before income taxes	(1,241)	(406)	(2,041)	10,636
Provision for (benefit from) income taxes	26		44	1,581
Income (Loss) from Continuing Operations	(1,267)	(406)	(2,085)	9,055
Income from discontinued operations, including gain on sale - net of tax
Net income (loss)				9,055
Less: Net income attributable to noncontrolling interest
Net income (loss) attributable to Arch Coal, Inc.	(1,267)	(406)	(2,085)	9,055
Total comprehensive income (loss)	(1,267)	(406)	(2,085)	9,055
Eliminations [Member]
Condensed Financial Statement Line Items
Revenues
Costs, expenses and other
Cost of sales (exclusive of items shown separately below)
Depreciation, depletion and amortization
Amortization of acquired sales contracts, net
Change in fair value of coal derivatives and coal trading activities, net
Asset impairment and mine closure costs
Legal contingencies
Goodwill impairment
Selling, general and administrative expenses
Other operating income, net
Operating Expenses
Loss from investment in subsidiaries	61,537	(164,152)	42,199	324,429
Income (loss) from operations	61,537	(164,152)	42,199	324,429
Interest expense, net
Interest expense	26,204	23,386	72,528	63,838
Interest and investment income	(26,204)	(23,386)	(72,528)	(63,838)
Interest expense, net
Other Nonoperating Income (Expense) [Abstract]
Net loss resulting from early retirement and refinancing of debt
Income (loss) before income taxes	61,537	(164,152)	42,199	324,429
Provision for (benefit from) income taxes
Income (Loss) from Continuing Operations	61,537	(164,152)	42,199	324,429
Income from discontinued operations, including gain on sale - net of tax
Net income (loss)				324,429
Less: Net income attributable to noncontrolling interest
Net income (loss) attributable to Arch Coal, Inc.	61,537	(164,152)	42,199	324,429
Total comprehensive income (loss)	$ 60,508	$ (162,969)	$ 41,260	$ 327,593

Supplemental Condensed Consolidating Financial Information (Schedule Of Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Assets
Cash and cash equivalents	$ 1,133,128	$ 784,622	$ 550,756	$ 138,149
Restricted cash		3,453
Short term investments	248,724	234,305
Receivables	214,839	332,080
Inventories	287,409	365,424
Other	145,539	194,220
Total current assets	2,029,639	1,914,104
Property, plant and equipment, net	6,778,225	7,337,098
Investment in subsidiaries
Intercompany receivables
Note receivable from Arch Western
Other	723,591	755,575
Assets, Noncurrent	723,591	755,575
Total assets	9,531,455	10,006,777	9,935,854
Liabilities and Stockholders’ Equity
Accounts payable	207,273	224,418
Accrued expenses and other current liabilities	349,454	319,755
Current maturities of debt	23,050	32,896
Total current liabilities	579,777	577,069
Long-term debt	5,074,384	5,085,879
Intercompany payables
Note payable to Arch Coal
Asset retirement obligations	411,121	409,705
Accrued pension benefits	68,539	67,630
Accrued postretirement benefits other than pension	44,279	45,086
Accrued workers’ compensation	82,014	81,629
Deferred income taxes	484,130	664,182
Other noncurrent liabilities	205,557	221,030
Total liabilities	6,949,801	7,152,210
Stockholders' equity	2,581,654	2,854,567
Total liabilities and stockholders’ equity	9,531,455	10,006,777
Parent/Issuer [Member]
Assets
Cash and cash equivalents	1,021,245	671,313	313,548	66,542
Restricted cash		3,453
Short term investments	248,724	234,305
Receivables	7,847	49,281
Inventories
Other	96,992	106,786
Total current assets	1,374,808	1,065,138
Property, plant and equipment, net	25,526	27,476
Investment in subsidiaries	7,992,601	8,254,508
Intercompany receivables
Note receivable from Arch Western	675,000	675,000
Other	147,950	187,171
Assets, Noncurrent	8,815,551	9,116,679
Total assets	10,215,885	10,209,293
Liabilities and Stockholders’ Equity
Accounts payable	20,728	19,859
Accrued expenses and other current liabilities	107,756	65,293
Current maturities of debt	19,343	32,054
Total current liabilities	147,827	117,206
Long-term debt	5,055,021	5,061,925
Intercompany payables	1,810,718	1,367,739
Note payable to Arch Coal
Asset retirement obligations	1,150	1,646
Accrued pension benefits	36,304	33,456
Accrued postretirement benefits other than pension	14,267	13,953
Accrued workers’ compensation	25,601	25,323
Deferred income taxes	484,130	664,182
Other noncurrent liabilities	59,179	69,296
Total liabilities	7,634,197	7,354,726
Stockholders' equity	2,581,688	2,854,567
Total liabilities and stockholders’ equity	10,215,885	10,209,293
Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents	100,410	100,468	225,431	70,258
Restricted cash
Short term investments
Receivables	21,178	40,452
Inventories	287,409	365,424
Other	48,270	86,877
Total current assets	457,267	593,221
Property, plant and equipment, net	6,752,687	7,309,550
Investment in subsidiaries
Intercompany receivables	1,986,992	1,600,311
Note receivable from Arch Western
Other	575,551	568,314
Assets, Noncurrent	2,562,543	2,168,625
Total assets	9,772,497	10,071,396
Liabilities and Stockholders’ Equity
Accounts payable	186,468	204,370
Accrued expenses and other current liabilities	246,063	259,162
Current maturities of debt	3,707	842
Total current liabilities	436,238	464,374
Long-term debt	19,363	23,954
Intercompany payables
Note payable to Arch Coal	675,000	675,000
Asset retirement obligations	409,971	408,059
Accrued pension benefits	32,235	34,174
Accrued postretirement benefits other than pension	30,012	31,133
Accrued workers’ compensation	56,413	56,306
Deferred income taxes
Other noncurrent liabilities	146,055	151,360
Total liabilities	1,805,287	1,844,360
Stockholders' equity	7,967,210	8,227,036
Total liabilities and stockholders’ equity	9,772,497	10,071,396
Non-Guarantor Subsidiaries [Member]
Assets
Cash and cash equivalents	11,473	12,841	11,777	1,349
Restricted cash
Short term investments
Receivables	190,493	247,171
Inventories
Other	277	557
Total current assets	202,243	260,569
Property, plant and equipment, net	46	72
Investment in subsidiaries
Intercompany receivables
Note receivable from Arch Western
Other	90	90
Assets, Noncurrent	90	90
Total assets	202,379	260,731
Liabilities and Stockholders’ Equity
Accounts payable	77	189
Accrued expenses and other current liabilities	314	124
Current maturities of debt
Total current liabilities	391	313
Long-term debt
Intercompany payables	176,274	232,572
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	323	374
Total liabilities	176,988	233,259
Stockholders' equity	25,391	27,472
Total liabilities and stockholders’ equity	202,379	260,731
Eliminations [Member]
Assets
Cash and cash equivalents
Restricted cash
Short term investments
Receivables	(4,679)	(4,824)
Inventories
Other
Total current assets	(4,679)	(4,824)
Property, plant and equipment, net	(34)
Investment in subsidiaries	(7,992,601)	(8,254,508)
Intercompany receivables	(1,986,992)	(1,600,311)
Note receivable from Arch Western	(675,000)	(675,000)
Other
Assets, Noncurrent	(10,654,593)	(10,529,819)
Total assets	(10,659,306)	(10,534,643)
Liabilities and Stockholders’ Equity
Accounts payable
Accrued expenses and other current liabilities	(4,679)	(4,824)
Current maturities of debt
Total current liabilities	(4,679)	(4,824)
Long-term debt
Intercompany payables	(1,986,992)	(1,600,311)
Note payable to Arch Coal	(675,000)	(675,000)
Asset retirement obligations
Accrued pension benefits
Accrued postretirement benefits other than pension
Accrued workers’ compensation
Deferred income taxes
Other noncurrent liabilities
Total liabilities	(2,666,671)	(2,280,135)
Stockholders' equity	(7,992,635)	(8,254,508)
Total liabilities and stockholders’ equity	$ (10,659,306)	$ (10,534,643)

Supplemental Condensed Consolidating Financial Information (Schedule Of Condensed Consolidating Statements Of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Cash provided by (used in) operating activities			$ 186,592	$ 356,395
Investing Activities
Capital expenditures	$ (54,104)	$ (101,895)	(223,168)	(303,968)
Minimum royalty payments			(10,901)	(9,192)
Proceeds from dispositions of property, plant and equipment			8,799	22,624
Proceeds from sale-leaseback transactions			34,919
Proceeds from sale of Canyon Fuel			422,663
Purchases of short term investments			(85,418)	(99,628)
Proceeds from sales of short term investments			67,255
Investments in and advances to affiliates			(11,124)	(12,685)
Purchase of noncontrolling interest				(17,500)
Change in restricted cash			3,453	6,872
Cash provided by (used in) investing activities			206,478	(413,477)
Financing Activities
Contributions from parent
Proceeds from issuance of term loan				1,386,000
Payments on term loan			(12,375)	(3,500)
Payments to retire debt			(384)	(452,806)
Net decrease in borrowings under lines of credit				(381,300)
Net payments on other debt			(12,700)	(13,078)
Debt financing costs				(34,686)
Dividends paid			(19,105)	(36,072)
Proceeds from exercise of options under incentive plans				5,131
Transactions with affiliates, net
Cash provided by (used in) financing activities			(44,564)	469,689
Increase (decrease) in cash and cash equivalents			348,506	412,607
Cash and cash equivalents, beginning of period			784,622	138,149
Cash and cash equivalents, end of period	1,133,128	550,756	1,133,128	550,756
Parent/Issuer [Member]
Cash provided by (used in) operating activities			(22,206)	(610,129)
Investing Activities
Capital expenditures			(2,488)	(4,150)
Minimum royalty payments
Proceeds from dispositions of property, plant and equipment
Proceeds from sale-leaseback transactions
Proceeds from sale of Canyon Fuel
Purchases of short term investments			(85,418)	(99,628)
Proceeds from sales of short term investments			67,255
Investments in and advances to affiliates			(4,016)	(5,138)
Purchase of noncontrolling interest
Change in restricted cash			3,453	6,872
Cash provided by (used in) investing activities			(21,214)	(102,044)
Financing Activities
Contributions from parent
Proceeds from issuance of term loan				1,386,000
Payments on term loan			(12,375)	(3,500)
Payments to retire debt
Net decrease in borrowings under lines of credit				(375,000)
Net payments on other debt			(12,700)	(13,078)
Debt financing costs				(34,640)
Dividends paid			(19,105)	(36,072)
Proceeds from exercise of options under incentive plans				5,131
Transactions with affiliates, net			437,532	30,338
Cash provided by (used in) financing activities			393,352	959,179
Increase (decrease) in cash and cash equivalents			349,932	247,006
Cash and cash equivalents, beginning of period			671,313	66,542
Cash and cash equivalents, end of period	1,021,245	313,548	1,021,245	313,548
Guarantor Subsidiaries [Member]
Cash provided by (used in) operating activities			153,868	874,545
Investing Activities
Capital expenditures			(220,680)	(299,818)
Minimum royalty payments			(10,901)	(9,192)
Proceeds from dispositions of property, plant and equipment			8,799	1,127
Proceeds from sale-leaseback transactions			34,919
Proceeds from sale of Canyon Fuel			422,663
Purchases of short term investments
Proceeds from sales of short term investments
Investments in and advances to affiliates			(7,492)	(9,082)
Purchase of noncontrolling interest				(17,500)
Change in restricted cash
Cash provided by (used in) investing activities			227,308	(334,465)
Financing Activities
Contributions from parent			384	1,535
Proceeds from issuance of term loan
Payments on term loan
Payments to retire debt			(384)	(452,806)
Net decrease in borrowings under lines of credit
Net payments on other debt
Debt financing costs
Dividends paid
Proceeds from exercise of options under incentive plans
Transactions with affiliates, net			(381,234)	66,364
Cash provided by (used in) financing activities			(381,234)	(384,907)
Increase (decrease) in cash and cash equivalents			(58)	155,173
Cash and cash equivalents, beginning of period			100,468	70,258
Cash and cash equivalents, end of period	100,410	225,431	100,410	225,431
Non-Guarantor Subsidiaries [Member]
Cash provided by (used in) operating activities			54,930	91,979
Investing Activities
Capital expenditures
Minimum royalty payments
Proceeds from dispositions of property, plant and equipment				21,497
Proceeds from sale-leaseback transactions
Proceeds from sale of Canyon Fuel
Purchases of short term investments
Proceeds from sales of short term investments
Investments in and advances to affiliates
Purchase of noncontrolling interest
Change in restricted cash
Cash provided by (used in) investing activities				21,497
Financing Activities
Contributions from parent
Proceeds from issuance of term loan
Payments on term loan
Payments to retire debt
Net decrease in borrowings under lines of credit				(6,300)
Net payments on other debt
Debt financing costs				(46)
Dividends paid
Proceeds from exercise of options under incentive plans
Transactions with affiliates, net			(56,298)	(96,702)
Cash provided by (used in) financing activities			(56,298)	(103,048)
Increase (decrease) in cash and cash equivalents			(1,368)	10,428
Cash and cash equivalents, beginning of period			12,841	1,349
Cash and cash equivalents, end of period	11,473	11,777	11,473	11,777
Eliminations [Member]
Cash provided by (used in) operating activities
Investing Activities
Capital expenditures
Minimum royalty payments
Proceeds from dispositions of property, plant and equipment
Proceeds from sale-leaseback transactions
Proceeds from sale of Canyon Fuel
Purchases of short term investments
Proceeds from sales of short term investments
Investments in and advances to affiliates			384	1,535
Purchase of noncontrolling interest
Change in restricted cash
Cash provided by (used in) investing activities			384	1,535
Financing Activities
Contributions from parent			(384)	(1,535)
Proceeds from issuance of term loan
Payments on term loan
Payments to retire debt
Net decrease in borrowings under lines of credit
Net payments on other debt
Debt financing costs
Dividends paid
Proceeds from exercise of options under incentive plans
Transactions with affiliates, net
Cash provided by (used in) financing activities			(384)	(1,535)
Increase (decrease) in cash and cash equivalents
Cash and cash equivalents, beginning of period
Cash and cash equivalents, end of period