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Document and Entity Information - USD ($) $ in Billions	12 Months Ended
Document and Entity Information - USD ($) $ in Billions	Dec. 31, 2017	Feb. 16, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	ARCH COAL INC
Entity Central Index Key	0001037676
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		20,986,812
Entity Well known seasoned issuer	Yes
Entity Voluntary Filers	No
Entity Current reporting status	Yes
Entity Public Float			$ 1.7

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Revenues	$ 575,688		$ 2,324,623
Costs, expenses and other operating
Cost of sales (exclusive of items shown separately below)	470,644		1,843,093
Depreciation, depletion and amortization	32,604		122,464
Accretion on asset retirement obligations	7,634		30,209
Amortization of sales contracts, net	796		53,985
Change in fair value of coal derivatives and coal trading activities, net	396		7,222
Asset impairment and mine closure costs	0		0
Losses from disposed operations resulting from Patriot Coal bankruptcy	0		0
Selling, general and administrative expenses	22,836		86,821
Gain on sale of Lone Mountain Processing, Inc.	0		(21,297)
Other operating (income) expense, net	(5,340)		(30,270)
Total operating expenses	529,570		2,092,227
Income (loss) from operations	46,118		232,396
Interest expense, net
Interest expense	(11,241)		(26,905)
Interest and investment income	487		2,649
Interest expense, net	(10,754)		(24,256)
Income (loss) before nonoperating expenses	35,364		208,140
Nonoperating income (expense)
Net loss resulting from early retirement of debt and debt restructuring	0		(2,547)
Reorganization income (loss), net	(759)		(2,398)
Nonoperating Income (Expense)	(759)		(4,945)
Income (loss) before income taxes	34,605		203,195
Provision for (benefit from) income taxes	1,156		(35,255)
Net income (loss)	$ 33,449		$ 238,450
Earnings (loss) per common share
Basic earnings (loss) per common share (in dollars per share)	$ 1.34		$ 10.05
Diluted earnings (loss) per common share (in dollars per share)	$ 1.31		$ 9.84
Weighted average shares outstanding
Basic weighted average shares outstanding (in shares)	25,002		23,725
Diluted weighted average shares outstanding (in shares)	25,469		24,240
Predecessor
Revenues		$ 1,398,709		$ 2,573,260
Costs, expenses and other operating
Cost of sales (exclusive of items shown separately below)		1,264,464		2,172,753
Depreciation, depletion and amortization		191,581		379,345
Accretion on asset retirement obligations		24,321		33,680
Amortization of sales contracts, net		(728)		(8,811)
Change in fair value of coal derivatives and coal trading activities, net		2,856		(1,583)
Asset impairment and mine closure costs		129,267		2,628,303
Losses from disposed operations resulting from Patriot Coal bankruptcy		0		116,343
Selling, general and administrative expenses		59,343		98,783
Gain on sale of Lone Mountain Processing, Inc.		0		0
Other operating (income) expense, net		(15,257)		19,510
Total operating expenses		1,655,847		5,438,323
Income (loss) from operations		(257,138)		(2,865,063)
Interest expense, net
Interest expense		(135,888)		(397,979)
Interest and investment income		2,653		4,430
Interest expense, net		(133,235)		(393,549)
Income (loss) before nonoperating expenses		(390,373)		(3,258,612)
Nonoperating income (expense)
Net loss resulting from early retirement of debt and debt restructuring		(2,213)		(27,910)
Reorganization income (loss), net		1,630,041		0
Nonoperating Income (Expense)		1,627,828		(27,910)
Income (loss) before income taxes		1,237,455		(3,286,522)
Provision for (benefit from) income taxes		(4,626)		(373,380)
Net income (loss)		$ 1,242,081		$ (2,913,142)
Earnings (loss) per common share
Basic earnings (loss) per common share (in dollars per share)		$ 58.33		$ (136.86)
Diluted earnings (loss) per common share (in dollars per share)		$ 58.28		$ (136.86)
Weighted average shares outstanding
Basic weighted average shares outstanding (in shares)		21,293		21,285
Diluted weighted average shares outstanding (in shares)		21,313		21,285

Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Net income (loss)	$ 33,449		$ 238,450
Derivative instruments
Comprehensive income (loss) before tax	0		647
Income tax benefit (provision)	0		0
Derivatives Qualifying as Hedges, Adjustment, Net of Tax	0		647
Pension, postretirement and other post-employment benefits
Comprehensive income (loss) before tax	24,067		(4,347)
Income tax benefit (provision)	0		0
Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	24,067		(4,347)
Available-for-sale securities
Comprehensive income (loss) before tax	387		(387)
Income tax benefit (provision)	0		0
Available-for-sale Securities Adjustment, Net of Tax	387		(387)
Total other comprehensive income (loss)	24,454		(4,087)
Total comprehensive income (loss)	$ 57,903		$ 234,363
Predecessor
Net income (loss)		$ 1,242,081		$ (2,913,142)
Derivative instruments
Comprehensive income (loss) before tax		(532)		(3,477)
Income tax benefit (provision)		80		1,252
Derivatives Qualifying as Hedges, Adjustment, Net of Tax		(452)		(2,225)
Pension, postretirement and other post-employment benefits
Comprehensive income (loss) before tax		(1,848)		(5,592)
Income tax benefit (provision)		483		2,011
Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax		(1,365)		(3,581)
Available-for-sale securities
Comprehensive income (loss) before tax		2,968		1,185
Income tax benefit (provision)		(1,042)		(435)
Available-for-sale Securities Adjustment, Net of Tax		1,926		750
Total other comprehensive income (loss)		109		(5,056)
Total comprehensive income (loss)		$ 1,242,190		$ (2,918,198)

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 273,387	$ 305,372
Short term investments	155,846	88,072
Restricted cash		71,050
Trade accounts receivable	172,604	184,483
Other receivables	29,771	19,877
Inventories	128,960	113,462
Other current assets	70,426	96,306
Total current assets	830,994	878,622
Property, plant and equipment
Coal lands and mineral rights	390,920	387,591
Plant and equipment	445,407	418,182
Deferred mine development	267,063	280,323
Property, plant and equipment, gross	1,103,390	1,086,096
Less accumulated depreciation, depletion and amortization	(147,442)	(32,493)
Property, plant and equipment, net	955,948	1,053,603
Other assets
Prepaid royalties	4,280	0
Deferred income taxes	22,520	0
Equity investments	106,107	96,074
Other noncurrent assets	59,783	108,298
Total other assets	192,690	204,372
Total assets	1,979,632	2,136,597
Current liabilities
Accounts payable	134,137	95,953
Accrued expenses and other current liabilities	184,161	205,240
Current maturities of debt	15,783	11,038
Total current liabilities	334,081	312,231
Long-term debt	310,134	351,841
Asset retirement obligations	308,855	337,227
Accrued pension benefits	14,036	38,884
Accrued postretirement benefits other than pension	102,369	101,445
Accrued workers’ compensation	184,835	184,568
Other noncurrent liabilities	59,457	63,824
Total liabilities	1,313,767	1,390,020
Stockholders' equity
Common stock, $0.01 par value, authorized 300,000 shares, issued 25,047 and 25,002 shares at December 31, 2017 and 2016, respectively	250	250
Paid-in capital	700,125	688,424
Treasury stock, 3,977 shares at December 31, 2017, at cost	(302,109)	0
Retained earnings	247,232	33,449
Accumulated other comprehensive income (loss)	20,367	24,454
Total stockholders’ equity	665,865	746,577
Total liabilities and stockholders’ equity	$ 1,979,632	$ 2,136,597

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	300,000,000	26,000,000
Common stock, shares issued	25,047,000	25,002,000
Treasury stock, shares	3,977,000	0

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Operating activties
Net income (loss)	$ 33,449		$ 238,450
Adjustments to reconcile net income (loss) to cash provided by (used in) operating activities:
Depreciation, depletion and amortization	32,604		122,464
Accretion on asset retirement obligations	7,634		30,209
Amortization of sales contracts, net	796		53,985
Prepaid royalties expensed	2,587		2,905
Deferred income taxes	3		(21,965)
Employee stock-based compensation expense	1,032		10,437
Gains on disposals and divestitures	(485)		(24,327)
Asset impairment and noncash mine closure costs	0		0
Losses from disposed operations resulting from Patriot Coal bankruptcy	0		0
Amortization relating to financing activities	467		3,736
Net loss resulting from early retirement of debt and debt restructuring	0		2,547
Non-cash bankruptcy reorganization items	0		0
Changes in:
Receivables	(22,196)		8,370
Inventories	24,870		(19,626)
Coal derivative assets and liabilities	1,662		6,040
Accounts payable, accrued expenses and other current liabilities	34,129		17,173
Asset retirement obligations	(4,535)		(20,584)
Pension, postretirement and other postemployment benefits	(5,625)		(15,253)
Other	(22,200)		1,912
Cash provided by (used in) operating activities	84,192		396,473
Investing activities
Capital expenditures	(15,214)		(59,205)
Minimum royalty payments	(63)		(5,296)
Proceeds from disposals and divestitures	572		12,920
Purchases of short term investments	0		(258,948)
Proceeds from sales of short term investments	23,000		190,064
Proceeds from sale of investments in equity investments and securities	0		0
Investments in and advances to affiliates, net	(823)		(10,173)
Withdrawals (deposits) of restricted cash	10,512		70,836
Cash provided by (used in) investing activities	17,984		(59,802)
Financing activities
Proceeds from issuance of term loan due 2024	0		298,500
Payments to extinguish term loan due 2021	0		(325,684)
Payments on term loan	(816)		(2,250)
Net receipts (payments) on other debt	3,374		(694)
Debt financing costs	0		(10,149)
Dividends paid	0		(24,369)
Purchases of treasury stock	0		(301,512)
Expenses related to debt restructuring	0		(2,360)
Other	151		(138)
Cash provided by (used in) financing activities	2,709		(368,656)
Increase (decrease) in cash and cash equivalents	104,885		(31,985)
Cash and cash equivalents, beginning of period	200,487		305,372
Cash and cash equivalents, end of period	305,372	$ 200,487	273,387
SUPPLEMENTAL CASH FLOW INFORMATION
Cash paid during the period for interest	39,620		34,691
Cash refunded during the period for income taxes, net	287		$ 7,958
Predecessor
Operating activties
Net income (loss)		1,242,081		$ (2,913,142)
Adjustments to reconcile net income (loss) to cash provided by (used in) operating activities:
Depreciation, depletion and amortization		191,581		379,345
Accretion on asset retirement obligations		24,321		33,680
Amortization of sales contracts, net		(728)		(8,811)
Prepaid royalties expensed		4,791		8,109
Deferred income taxes		(419)		(367,210)
Employee stock-based compensation expense		2,096		5,760
Gains on disposals and divestitures		(6,628)		(2,270)
Asset impairment and noncash mine closure costs		119,194		2,613,345
Losses from disposed operations resulting from Patriot Coal bankruptcy		0		116,343
Amortization relating to financing activities		12,800		25,241
Net loss resulting from early retirement of debt and debt restructuring		2,213		27,910
Non-cash bankruptcy reorganization items		(1,775,910)		0
Changes in:
Receivables		(42,786)		98,212
Inventories		34,440		(6,534)
Coal derivative assets and liabilities		5,678		973
Accounts payable, accrued expenses and other current liabilities		15,316		(15,532)
Asset retirement obligations		(12,041)		(17,040)
Pension, postretirement and other postemployment benefits		(15,692)		4,800
Other		(28,525)		(27,546)
Cash provided by (used in) operating activities		(228,218)		(44,367)
Investing activities
Capital expenditures		(82,434)		(119,024)
Minimum royalty payments		(305)		(5,871)
Proceeds from disposals and divestitures		(2,921)		2,191
Purchases of short term investments		(98,750)		(246,735)
Proceeds from sales of short term investments		185,859		290,205
Proceeds from sale of investments in equity investments and securities		1,147		2,259
Investments in and advances to affiliates, net		(3,441)		(11,502)
Withdrawals (deposits) of restricted cash		15,979		(91,864)
Cash provided by (used in) investing activities		15,134		(180,341)
Financing activities
Proceeds from issuance of term loan due 2024		0		0
Payments to extinguish term loan due 2021		0		0
Payments on term loan		0		(19,500)
Net receipts (payments) on other debt		(11,986)		(11,332)
Debt financing costs		(23,011)		0
Dividends paid		0		0
Purchases of treasury stock		0		0
Expenses related to debt restructuring		(2,213)		(27,910)
Other		0		0
Cash provided by (used in) financing activities		(37,210)		(58,742)
Increase (decrease) in cash and cash equivalents		(250,294)		(283,450)
Cash and cash equivalents, beginning of period	$ 200,487	450,781		734,231
Cash and cash equivalents, end of period		200,487		450,781
SUPPLEMENTAL CASH FLOW INFORMATION
Cash paid during the period for interest		79,979		283,337
Cash refunded during the period for income taxes, net		$ 49		$ 4,138

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Paid-in Capital	Treasury Stock, at cost	Retained Earnings (Accumulated Deficit)	Accumulated Other Comprehensive Income (Loss)
Beginning Balance (Predecessor) at Dec. 31, 2014	$ 1,668,154	$ 2,141	$ 3,048,460	$ (53,863)	$ (1,331,825)	$ 3,241
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss) \| Predecessor	(2,918,198)				(2,913,142)	(5,056)
Issuance of 64 shares of common stock under the stock incentive plan-restricted stock and restricted stock units, net of forfeitures \| Predecessor	(5)	4	(9)
Employee stock-based compensation expense \| Predecessor	5,760		5,760
Ending Balance (Predecessor) at Dec. 31, 2015	(1,244,289)	2,145	3,054,211	(53,863)	(4,244,967)	(1,815)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss) \| Predecessor	1,242,190	0	0		1,242,081	109
Employee stock-based compensation expense \| Predecessor	2,099		2,099
Elimination of predecessor equity \| Predecessor	0	(2,145)	(3,056,310)	53,863	3,002,886	1,706
Ending Balance (Predecessor) at Oct. 01, 2016	0	0	0	0	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	57,903				33,449	24,454
Employee stock-based compensation expense	1,032		1,032
Issuance of successor equity	687,483	250	687,233
Warrants exercised	159		159
Ending Balance at Dec. 31, 2016	746,577	250	688,424	0	33,449	24,454
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	234,363				238,450	(4,087)
Issuance of 64 shares of common stock under the stock incentive plan-restricted stock and restricted stock units, net of forfeitures	1,244		1,244
Employee stock-based compensation expense	10,437		10,437
Dividends on common shares ($0.35/share)	(24,667)				(24,667)
Warrants exercised	20		20
Purchase of 3,977,215 shares of common stock under share repurchase program	(302,109)			(302,109)
Ending Balance at Dec. 31, 2017	$ 665,865	$ 250	$ 700,125	$ (302,109)	$ 247,232	$ 20,367

Consolidated Statements of Stockholders' Equity (Deficit) (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2015
Dividends (in dollars per share)	$ 1.05
Predecessor
shares issued stock plans RS and RSU		64,000
Successor
shares issued stock plans RS and RSU	17,233
Dividends (in dollars per share)	$ 0.35
Purchase of 3,977,215 shares of common stock under share repurchase program	3,977,215

Basis of Presentation	12 Months Ended
Basis of Presentation	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements include the accounts of Arch Coal, Inc. and its subsidiaries and controlled entities (the “Company”). Unless the context indicates otherwise, the terms “Arch” and the “Company” are used interchangeably in this Annual Report on Form 10-K refer to both the Predecessor and Successor 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, Illinois, Wyoming and Colorado. All subsidiaries are wholly-owned. Intercompany transactions and accounts have been eliminated in consolidation. Chapter 11 Filing and Emergence from Bankruptcy On January 11, 2016 (the “Petition Date”), Arch and substantially all of its wholly owned domestic subsidiaries (the “Filing Subsidiaries” and, together with Arch, the “Debtors”) filed voluntary petitions for reorganization (collectively, the “Bankruptcy Petitions”) under Chapter 11 of Title 11 of the U.S. Code (the “Bankruptcy Code”) in the United States Bankruptcy Court for the Eastern District of Missouri (the “Court”). The Debtor’s Chapter 11 Cases (collectively, the “Chapter 11 Cases”) were jointly administered under the caption In re Arch Coal, Inc., et al. Case No. 16-40120 (lead case). During the bankruptcy proceedings, each Debtor operated its business as a “debtor in possession” under the jurisdiction of the Court and in accordance with the applicable provisions of the Bankruptcy Code and the orders of the Court. For periods subsequent to filing the Bankruptcy Petitions, the Company applied the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 852, “Reorganizations”, in preparing its consolidated financial statements. ASC 852 requires that financial statements distinguish transactions and events that are directly associated with the reorganization from the ongoing operations of the business. Accordingly, certain revenues, expenses, realized gains and losses and provisions for losses that are realized or incurred in the bankruptcy proceedings have been recorded in a reorganization line item on the Consolidated Statement of Operations. In addition, the pre-petition obligations that may be impacted by the bankruptcy reorganization process were classified on the balance sheet as liabilities subject to compromise. On September 13, 2016, the Bankruptcy Court entered an order, Docket No. 1324, confirming the Debtors’ Fourth Amended Joint Plan of Reorganization under Chapter 11 of the Bankruptcy Code dated as of September 11, 2016 (the “Plan”), which order was amended on September 15, 2016, Docket No. 1334. On October 5, 2016, Arch Coal satisfied the closing conditions contemplated by the Plan, which became effective on that date (the “Effective Date”). On the Plan Effective Date, the Company applied fresh start accounting which required the Company to allocate its reorganization value to the fair value of assets and liabilities in conformity with the guidance for the acquisition method of accounting for business combinations. In addition to fresh start accounting, the Company’s consolidated financial statements reflect all impacts of the transactions contemplated by the Plan. Under the provisions of fresh start accounting, a new entity has been created for financial reporting purposes. The Company selected an accounting convenience date of October 1, 2016 for purposes of applying fresh start accounting as the activity between the convenience date and the Effective Date does not result in a material difference in the results. References to “Successor” in the financial statements and accompanying footnotes are in reference to reporting dates on or after October 2, 2016; references to “Predecessor” in the financial statements and accompanying footnotes are in reference to reporting dates through October 1, 2016 which includes the impact of the Plan provisions and the application of fresh start accounting. As such, the Company’s financial statements for the Successor will not be comparable in many respects to its financial statements for periods prior to the adoption of fresh start accounting and prior to the accounting for the effects of the Plan.

Accounting Policies	12 Months Ended
Accounting Policies	Dec. 31, 2017
Accounting Policies [Abstract]
Accounting Policies	Accounting Policies The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States for financial reporting and U.S. Securities and Exchange Commission regulations. Accounting Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and revenues and expenses in the accompanying consolidated financial statements and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates. Cash and Cash Equivalents Cash and cash equivalents are stated at cost. Cash equivalents consist of highly-liquid investments with an original maturity of three months or less when purchased. Restricted cash Restricted cash represents cash collateral supporting letters of credit issued under the Company’s accounts receivable securitization program. Accounts Receivable Accounts receivable are recorded at amounts that are expected to be collected, based on past collection history, the economic environment and specified risks identified in the receivables portfolio. Inventories Coal and supplies inventories are valued at the lower of average cost or market. Coal inventory costs include labor, supplies, equipment costs, transportation costs incurred prior to the transfer of title to customers and operating overhead. The costs of removing overburden, called stripping costs, incurred during the production phase of the mine are considered variable production costs and are included in the cost of the coal extracted during the period the stripping costs are incurred. Investments and Membership Interests in Joint Ventures Investments and membership interests in joint ventures are accounted for under the equity method of accounting if the Company has the ability to exercise significant influence, but not control, over the entity. The Company’s share of the entity’s income or loss is reflected in “Other operating expense (income), net” in the consolidated statements of operations. Information about investment activity is provided in Note 10 to the Consolidated Financial Statements, “Equity Method Investments and Membership Interests in Joint Ventures.” Investments in debt securities and marketable equity securities that do not qualify for equity method accounting are classified as available-for-sale and are recorded at their fair values. Unrealized gains and losses on these investments are recorded in other comprehensive income or loss. A decline in the value of an investment that is considered other-than-temporary would be recognized in operating expenses. Sales Contracts Coal supply agreements (sales contracts) valued during fresh start accounting or acquired in a business combination are capitalized at their fair value and amortized over the tons of coal shipped during the term of the contract. The fair value of a sales contract is determined by discounting the cash flows attributable to the difference between the contract price and the prevailing forward prices for the tons under contract at the date of acquisition. See Note 11 to the Consolidated Financial Statements, “Sales Contracts” for further information related to the Company’s sales contracts. Exploration Costs Costs to acquire permits for exploration activities are capitalized. Drilling and other costs related to locating coal deposits and evaluating the economic viability of such deposits are expensed as incurred. Prepaid Royalties Leased mineral rights are often acquired through royalty payments. When royalty payments represent prepayments recoupable against royalties owed on future revenues from the underlying coal, they are recorded as a prepaid asset, with amounts expected to be recouped within one year classified as current. When coal from these leases is sold, the royalties owed are recouped against the prepayment and charged to cost of sales. An impairment charge is recognized for prepaid royalties that are not expected to be recouped. Property, Plant and Equipment Plant and Equipment Plant and equipment were recorded at fair value at emergence during fresh start accounting; subsequent purchases of property, plant and equipment have been recorded at cost. Interest costs incurred during the construction period for major asset additions are capitalized. The Company did not capitalize any interest costs during years ended December 31, 2017 and 2016, respectively. Expenditures that extend the useful lives of existing plant and equipment or increase the productivity of the asset are capitalized. The cost of maintenance and repairs that do not extend the useful life or increase the productivity of the asset is expensed as incurred. Preparation plants and loadouts are depreciated using the units-of-production method over the estimated recoverable reserves, subject to a minimum level of depreciation. Other plant and equipment are depreciated principally using the straight-line method over the estimated useful lives of the assets, limited by the remaining life of the mine. The useful lives of mining equipment, including longwalls, draglines and shovels, range from 7 to 18 years. The useful lives of buildings and leasehold improvements generally range from 1 to 21 years. Deferred Mine Development Costs of developing new mines or significantly expanding the capacity of existing mines are capitalized and amortized using the units-of-production method over the estimated recoverable reserves that are associated with the property being benefited. Costs may include construction permits and licenses; mine design; construction of access roads, shafts, slopes and main entries; and removing overburden to access reserves in a new pit. Additionally, deferred mine development includes the asset cost associated with asset retirement obligations. Coal sales revenue related to incidental production during the development phase will be recorded as coal sales revenue with an offset to cost of coal sales based on the estimated cost per ton sold for the mine when the asset is in place for its intended use. Coal Lands and Mineral Rights Rights to coal reserves may be acquired directly through governmental or private entities. A significant portion of the Company’s coal reserves are controlled through leasing arrangements. Lease agreements are generally long-term in nature (original terms range from 10 to 50 years), and substantially all of the leases contain provisions that allow for automatic extension of the lease term providing certain requirements are met. The net book value of the Company’s coal interests was $361.2 million and $381.0 million at December 31, 2017 and 2016, respectively. Payments to acquire royalty lease agreements and lease bonus payments are capitalized as a cost of the underlying mineral reserves and depleted over the life of proven and probable reserves. Coal lease rights are depleted using the units-of-production method, and the rights are assumed to have no residual value. The Company currently does not have any future lease bonus payments. Depreciation, depletion and amortization The depreciation, depletion and amortization related to long-lived assets is reflected in the statement of operations as a separate line item. No depreciation, depletion or amortization is included in any other operating cost categories. Impairment If facts and circumstances suggest that the carrying value of a long-lived asset or asset group may not be recoverable, the asset or asset group is reviewed for potential impairment. If this review indicates that the carrying amount of the asset will not be recoverable through projected undiscounted cash flows generated by the asset and its related asset group over its remaining life, then an impairment loss is recognized by reducing the carrying value of the asset to its fair value. The Company may, under certain circumstances, idle mining operations in response to market conditions or other factors. Because an idling is not a permanent closure, it is not considered an automatic indicator of impairment. See additional discussion in Note 6 to the Consolidated Financial Statements, “Impairment Charges and Mine Closure Costs.” Deferred Financing Costs The Company capitalizes costs incurred in connection with new borrowings, the establishment or enhancement of credit facilities and the issuance of debt securities. These costs are amortized as an adjustment to interest expense over the life of the borrowing or term of the credit facility using the interest method. Debt issuance costs related to a recognized liability are presented in the balance sheet as a direct reduction from the carrying amount of that liability whereas debt issuance costs related to a credit facility with no balance outstanding are shown as an asset. The unamortized balance of deferred financing costs shown as an asset was $5.3 million at December 31, 2017, with $2.3 million classified as current; the unamortized balance of deferred financing costs shown as an asset at December 31, 2016 was $5.2 million with $1.9 million classified as current. The current amounts are classified within “Other current assets” and the noncurrent amounts are classified within “Other noncurrent assets.” For information on the unamortized balance of deferred financing fees related to outstanding debt, see Note 14 to the Consolidated Financial Statements, “Debt and Financing Arrangements.” Revenue Recognition Revenues include sales to customers of coal produced at Company operations and coal purchased from third parties. The Company recognizes revenue at the time risk of loss passes to the customer at contracted amounts. Transportation costs are included in cost of sales and amounts billed by the Company to its customers for transportation are included in revenues. Other Operating Expense (Income), net Other operating expense (income), net in the accompanying consolidated statements of operations reflects income and expense from sources other than physical coal sales, including: bookouts, or the practice of offsetting purchase and sale contracts for shipping convenience purposes; contract settlements; liquidated damage charges related to unused terminal and port capacity; royalties earned from properties leased to third parties; income from equity investments (Note 10, “Equity Method Investments and Membership Interests in Joint Ventures”); non-material gains and losses from divestitures and dispositions of assets; and realized gains and losses on derivatives that do not qualify for hedge accounting and are not held for trading purposes (Note 12, “Derivatives”). Asset Retirement Obligations The Company’s legal obligations associated with the retirement of long-lived assets are recognized at fair value at the time the obligations are incurred. Accretion expense is recognized through the expected settlement date of the obligation. Obligations are incurred at the time development of a mine commences for underground and surface mines or construction begins for support facilities, refuse areas and slurry ponds. The obligation’s fair value is determined using a discounted cash flow technique and is based upon permit requirements and various estimates and assumptions that would be used by market participants, including estimates of disturbed acreage, reclamation costs and assumptions regarding equipment productivity. Upon initial recognition of a liability, a corresponding amount is capitalized as part of the carrying value of the related long-lived asset. The Company reviews its asset retirement obligation at least annually and makes necessary adjustments for permit changes as granted by state authorities and for revisions of estimates of the amount and timing of costs. For ongoing operations, adjustments to the liability result in an adjustment to the corresponding asset. For idle operations, adjustments to the liability are recognized as income or expense in the period the adjustment is recorded. Any difference between the recorded obligation and the actual cost of reclamation is recorded in profit or loss in the period the obligation is settled. See additional discussion in Note 16, “Asset Retirement Obligations.” Loss 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. The amount accrued represents the Company’s best estimate of the loss, or, if no best estimate within a range of outcomes exists, the minimum amount in the range. Derivative Instruments The Company generally utilizes derivative instruments to manage exposures to commodity prices and interest rate risk on long-term debt. Additionally, the Company may hold certain coal derivative instruments for trading purposes. Derivative financial instruments are recognized in the balance sheet at fair value. Certain coal contracts may meet the definition of a derivative instrument, but because they provide for the physical purchase or sale of coal in quantities expected to be used or sold by the Company over a reasonable period in the normal course of business, they are not recognized on the balance sheet. Certain derivative instruments are designated as the hedge instrument in a hedging relationship. In a fair value hedge, the Company hedges the risk of changes in the fair value of a firm commitment, typically a fixed-price coal sales contract. Changes in both the hedged firm commitment and the fair value of a derivative used as a hedge instrument in a fair value hedge are recorded in earnings. In a cash flow hedge, the Company hedges the risk of changes in future cash flows related to the underlying item being hedged. Changes in the fair value of the derivative instrument used as a hedge instrument in a cash flow hedge are recorded in other comprehensive income or loss. Amounts in other comprehensive income or loss are reclassified to earnings when the hedged transaction affects earnings and are classified in a manner consistent with the transaction being hedged. The Company formally documents the relationships between hedging instruments and the respective hedged items, as well as its risk management objectives for hedge transactions. The Company evaluates the effectiveness of its hedging relationships both at the hedge’s inception and on an ongoing basis. Any ineffective portion of the change in fair value of a derivative instrument used as a hedge instrument in a fair value or cash flow hedge is recognized immediately in earnings. The ineffective portion is based on the extent to which exact offset is not achieved between the change in fair value of the hedge instrument and the cumulative change in expected future cash flows on the hedged transaction from inception of the hedge in a cash flow hedge or the change in the fair value. Ineffectiveness was insignificant for the periods disclosed within. See Note 12, “Derivatives” for further disclosures related to the Company’s derivative instruments. Fair Value Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly hypothetical transaction between market participants at a given measurement date. Valuation techniques used must maximize the use of observable inputs and minimize the use of unobservable inputs. See Note 17, “Fair Value Measurements” for further disclosures related to the Company’s recurring fair value estimates. Income Taxes Deferred income taxes are provided for temporary differences arising from differences between the financial statement and tax basis of assets and liabilities existing at each balance sheet date using enacted tax rates anticipated to be in effect when the related taxes are expected to be paid or recovered. A valuation allowance is established if it is more likely than not that a deferred tax asset will not be realized. Management reassesses the ability to realize its deferred tax assets annually in the fourth quarter or when circumstances indicate that the ability to realize deferred tax assets has changed. In determining the need for a valuation allowance, the Company considers projected realization of tax benefits based on expected levels of future taxable income, available tax planning strategies and the reversal of temporary differences. Benefits from tax positions that are uncertain are not recognized unless the Company concludes that it is more likely than not that the position would be sustained in a dispute with taxing authorities, should the dispute be taken to the court of last resort. The Company would measure any such benefit at the largest amount of benefit that is greater than 50 percent likely of being realized upon settlement with taxing authorities. See Note 15, “Taxes” for further disclosures about income taxes. Benefit Plans The Company has non-contributory defined benefit pension plans covering most of its salaried and hourly employees. On January 1, 2015 the Company’s cash balance and excess pension plans were amended to freeze new service credits for any new or active employee. The Company also currently provides certain postretirement medical and life insurance coverage for eligible employees. The cost of providing these benefits is determined on an actuarial basis and accrued over the employee’s period of active service. The Company recognizes the overfunded or underfunded status of these plans as determined on an actuarial basis on the balance sheet and the changes in the funded status are recognized in other comprehensive income. The Company amortizes actuarial gains and losses over the remaining service attribution periods of the employees using the corridor method. See Note 21, “Employee Benefit Plans” for additional disclosures relating to these obligations. Stock-Based Compensation The compensation cost of all stock-based awards is determined based on the grant-date fair value of the award, and is recognized over the requisite service period. The grant-date fair value of option awards and restricted stock awards with a market condition is determined using a Monte Carlo simulation. Compensation cost for an award with performance conditions is accrued if it is probable that the conditions will be met. The Company accounts for forfeitures as they occur. See further discussion in Note 19, “Stock-Based Compensation and Other Incentive Plans.” Recently Adopted Accounting Guidance In March 2016, the FASB issued Accounting Standards Update No. 2016-09, Compensation - Stock Compensation (Topic 718) ("ASU 2016-09"). ASU 2016-09 identifies areas for simplification involving several aspects of accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, an option to recognize gross stock compensation expense with actual forfeitures recognized as they occur, as well as certain classifications on the statement of cash flows. The Company adopted all provisions of this new accounting standard in the first quarter of 2017 and changed its forfeiture policy to recognize the impact of forfeitures when they occur from estimating expected forfeitures in determining stock-based compensation expense. There was no material impact to the Company's financial statements. Recent Accounting Guidance Issued Not Yet Effective In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers.” ASU 2014-09 is a comprehensive revenue recognition standard that will supersede nearly all existing revenue recognition guidance under current U.S. GAAP and replace it with a principle based approach for determining revenue recognition. ASU 2014-09 requires that companies recognize revenue based on the value of transferred goods or services as they occur in the contract. The ASU also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. ASU 2014-09 is effective for interim and annual periods beginning after December 15, 2017. The Company’s primary source of revenue is from the sale of coal through both short-term and long-term contracts with utilities, industrial customers and steel producers whereby revenue is currently recognized when risk of loss has passed to the customer. During the fourth quarter of 2017, the Company finalized its assessment related to the new standard by analyzing certain contracts representative of the majority of the Company’s coal sales and determined that the timing of revenue recognition related to the Company’s coal sales will remain consistent between the new standard and the current standard. The Company also reviewed other sources of revenue, and concluded the current basis of accounting for these items is in accordance with the new standard. The Company has concluded its adoption, using the modified retrospective method, will not have a material impact on its consolidated financial statements and there will be no cumulative adjustment to retained earnings. The Company also reviewed the disclosure requirements under the new standard and is compiling information needed for the expanded disclosures required during the first quarter of 2018. In February 2016, the FASB issued ASU No. 2016-02, “Leases” which, for operating leases, requires a lessee to recognize a right-of-use asset and a lease liability, initially measured at the present value of the lease payments, in its balance sheet. The standard also requires a lessee to recognize a single lease cost, calculated so that the cost of the lease is allocated over the term of the lease, on a generally straight line basis. The ASU is effective for public companies for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years; early adoption is permitted. The Company has both operating and capital leases. We expect the adoption of this standard to result in the recognition of right-of-use assets and lease liabilities not currently recorded on the Company’s financial statements. The Company is currently in the process of accumulating all contractual lease arrangements in order to determine the impact on its financial statements. In August 2016, the FASB issued ASU No. 2016-15, “Classification of Certain Cash Receipts and Cash Payments.” The amendment requires the classification of certain cash receipts and cash payments in the statement of cash flows to reduce diversity in practice. The new guidance will be effective for fiscal years beginning after December 15, 2017 and the interim periods therein, with early adoption permitted. The amendments in the classification should be applied retrospectively to all periods presented, unless deemed impracticable, in which case, the prospective application is permitted. The Company plans to adopt the guidance in this standard during the first quarter of 2018. In October 2016, the FASB issued ASU No. 2016-18, “Statement of Cash Flows-Restricted Cash.” The amendment requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning period and end of period total amounts shown on the statement of cash flows. ASU 2016-18 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years; early adoption is permitted. The Company plans to adopt the guidance in this standard during the first quarter of 2018. In March 2017, the FASB issued ASU No. 2017-07, “Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost.” Under the new guidance, employers will present the service cost component of the net periodic benefit cost in the same income statement line item(s) as other employee compensation costs arising from services rendered during the period. Employers will present the other components separately from the line item(s) that includes the service cost and outside of any subtotal of operating income, if one is presented. Employers will have to disclose the line(s) used to present the other components of net periodic benefit cost, if the components are not presented separately in the income statement. Additionally, only the service cost component will be eligible for capitalization in assets. ASU 2017-07 is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal year; early adoption is permitted. The Company plans to adopt the guidance in this standard during the first quarter of 2018. In August 2017, the FASB issued ASU No. 2017-12, “Targeted Improvements to Accounting for Hedging Activities.” The new guidance provides targeted improvements to the accounting for hedging activities to better align an entity’s risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedging results. ASU 2017-12 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years; early adoption is permitted. The Company anticipates early adopting the standard in the first quarter of 2018, although we do not expect a significant impact to the Company’s financial results.

Emergence from Bankruptcy and Fresh Start Accounting

12 Months Ended

Dec. 31, 2017

Reorganizations [Abstract]

Emergence from Bankruptcy and Fresh Start Accounting

On January 11, 2016 (the “Petition Date”), Arch and substantially all of its wholly owned domestic subsidiaries (the “Filing Subsidiaries” and, together with Arch, the “Debtors”) filed voluntary petitions for reorganization (collectively, the “Bankruptcy Petitions”) under Chapter 11 of Title 11 of the U.S. Code (the “Bankruptcy Code”) in the United States Bankruptcy Court for the Eastern District of Missouri (the “Court”). The Debtor’s Chapter 11 Cases (collectively, the “Chapter 11 Cases”) were jointly administered under the caption In re Arch Coal, Inc., et al. Case No. 16-40120 (lead case). During the bankruptcy proceedings, each Debtor operated its business as a “debtor in possession” under the jurisdiction of the Court and in accordance with the applicable provisions of the Bankruptcy Code and the orders of the Court.

For periods subsequent to filing the Bankruptcy Petitions, the Company applied the FASB Accounting Standards Codification (“ASC”) 852, “Reorganizations”, in preparing its consolidated financial statements. ASC 852 requires that financial statements distinguish transactions and events that are directly associated with the reorganization from the ongoing operations of the business. Accordingly, certain revenues, expenses, realized gains and losses and provisions for losses that are realized or incurred in the bankruptcy proceedings have been recorded in a reorganization line item on the Consolidated Statement of Operations. In addition, the pre-petition obligations that may be impacted by the bankruptcy reorganization process were classified on the balance sheet as liabilities subject to compromise.

On September 13, 2016, the Bankruptcy Court entered an order, Docket No. 1324, confirming the Debtors’ Fourth Amended Joint Plan of Reorganization under Chapter 11 of the Bankruptcy Code dated as of September 11, 2016 (the “Plan”), which order was amended on September 15, 2016, Docket No. 1334.

On October 5, 2016, Arch Coal satisfied the closing conditions contemplated by the Plan, which became effective on that date (the “Effective Date”).

On the Plan Effective Date, the Company applied fresh start accounting which required the Company to allocate its reorganization value to the fair value of assets and liabilities in conformity with the guidance for the acquisition method of accounting for business combinations. In addition to fresh start accounting, the Company’s consolidated financial statements reflect all impacts of the transactions contemplated by the Plan. Under the provisions of fresh start accounting, a new entity has been created for financial reporting purposes. The Company selected an accounting convenience date of October 1, 2016 for purposes of applying fresh start accounting as the activity between the convenience date and the Effective Date does not result in a material difference in the results. References to “Successor” in the financial statements and accompanying footnotes are in reference to reporting dates on or after October 2, 2016; references to “Predecessor” in the financial statements and accompanying footnotes are in reference to reporting dates through October 1, 2016 which includes the impact of the Plan provisions and the application of fresh start accounting. As such, the Company’s financial statements for the Successor will not be comparable in many respects to its financial statements for periods prior to the adoption of fresh start accounting and prior to the accounting for the effects of the Plan.

The following is a summary of certain provisions of the Plan, as confirmed by the Bankruptcy Court pursuant to the Confirmation Order, and is not intended to be a complete description of the Plan.

Treatment of Claims

The Plan contemplates that:


•	Holders of allowed administrative expense claims, priority claims (other than administrative expense claims and priority tax claims) and secured claims (other than claims arising under priority claims, the prepetition first lien credit facility and prepetition second lien notes) will be paid in full.

•

Holders of allowed claims arising under the Debtors’ prepetition first lien credit facility (“First Lien Credit Facility”) will receive their pro rata distribution of (i) total cash payments equal to the greater of (A) $144.8 million less the amount of the adequate protection payments and (B) $30 million; (ii) $326.5 million in principal amount of New First Lien Debt Facility; and (iii) 94% of the common stock of Reorganized Arch Coal (the “New Common Stock”), subject to dilution on account of (a) any Class A Common Stock (as defined below) issued upon exercise of the warrants (the “New Warrants”) issued pursuant to the Plan to purchase up to 12% of the fully diluted Class A Common Stock as of the Effective Date and exercisable at any time for a period of 7 years from the Effective Date at a strike price calculated based on a total equity capitalization of $1.425 billion ($57 per share) and (b) the issuance of New Common Stock in an amount of up to 10% of the New Common Stock, on a fully diluted basis, pursuant to a management incentive plan (the “Management Incentive Plan”).

•

Holders of allowed claims on account of prepetition second lien or unsecured notes (the “Prepetition Notes”) will receive their pro rata distribution of (i) $22.636 million in cash, (ii) at such holder’s election, either (A) such holder’s pro rata share of the New Warrants or (B) such holder’s pro rata share of $25 million in cash and (iii) 6% of the New Common Stock (subject to dilution on account of any exercise of the New Warrants and pursuant to the Management Incentive Plan).


•	Holders of allowed general unsecured claims against Debtors (other than claims on account of the First Lien Credit Facility or Prepetition Notes) will receive their pro rata distribution of $7.364 million cash, less fees and expenses incurred by any professionals retained by a claims oversight committee up to $200,000.

•

The Reorganized Debtors will waive and release any claims or causes of action that they have, had, or may have that are based on sections 502(d), 544, 545, 547, 548, 549, 550, 551, 553(b) and 724(a) of the Bankruptcy Code and analogous non-bankruptcy law for all purposes against (i) prepetition trade creditors and (ii) officers, directors, employees or representatives of the Debtors or the Reorganized Debtors and all agents and representatives of all of the foregoing. However, the Reorganized Debtors will retain the right to assert any said claims as defenses or counterclaims in any cause of action brought by any creditor.

Warrant Agreement

On the Effective Date, the Company entered into a warrant agreement (the “Warrant Agreement”) with American Stock Transfer & Trust Company, LLC as warrant agent and, pursuant to the terms of the Plan, issued warrants (“Warrants”) to purchase up to an aggregate of 1,914,856 shares of Class A Common Stock, par value $0.01 per share, of Arch Coal (the “Class A Common Stock”) to holders of claims arising under the Cancelled Notes (as defined below). Each Warrant expires on October 5, 2023, and is initially exercisable for one share of Class A Common Stock at an initial exercise price of $57.00 per share. The Warrants are exercisable by a holder paying the exercise price in cash or on a cashless basis, at the election of the holder. The Warrants contain anti-dilution adjustments for stock splits, reverse stock splits, stock dividends, dividends and distributions of cash, other securities or other property, spin-offs and tender and exchange offers by Arch Coal or its subsidiaries to purchase Class A Common Stock at above-market prices.

If, in connection with a merger, recapitalization, business combination, transfer to a third party of substantially all of Arch Coal’s consolidated assets or other transaction that results in a change to the Class A Common Stock (each, a “Transaction”), (i) the Transaction is consummated prior to the fifth anniversary of the Effective Date and the Transaction consideration to holders of Class A Common Stock is 90% or more listed common stock or common stock of a company that provides publicly available financial reporting, and holds management calls regarding the same, no less than quarterly (“Reporting Stock”) or (ii) regardless of the consideration, the Transaction is consummated on or after the fifth anniversary of the Effective Date, the Warrants will be assumed by the surviving company and will become exercisable for the consideration that the holders of Class A Common Stock receive in such Transaction; provided that if the consideration such holders receive consists solely of cash, then upon the consummation of such Transaction, Arch Coal will pay for each Warrant an amount of cash equal to the greater of (i) (x) the amount of cash payable with respect to the number of shares of Class A Common Stock underlying the Warrant minus (y) the exercise price per share then in effect multiplied by the number of shares of Class A Common Stock underlying the Warrant and (ii) $0.

If a Transaction is consummated prior to the fifth anniversary of the Effective Date in which the Transaction consideration is less than 90% Reporting Stock, a portion of the Warrants corresponding to the portion of the Transaction consideration that is Reporting Stock will be assumed by the surviving company and will become exercisable for the Reporting Stock consideration that the holders of Class A Common Stock receive in such Transaction, and the portion of the Warrants corresponding to the portion of the Transaction consideration that is not Reporting Stock will, at the option of each holder, (i) be assumed by the surviving company and will become exercisable for the consideration that the holders of Class A Common Stock receive in such Transaction or (ii) be redeemed by Arch Coal for cash in an amount equal to the Black Scholes Payment (as defined in the Warrant Agreement).

Termination of Material Definitive Agreements

On the Effective Date, by operation of the Plan, all outstanding obligations under the following notes issued by Arch Coal and guaranteed by certain subsidiary guarantors, (collectively, the “Cancelled Notes”) were cancelled and the indentures governing such obligations were cancelled except as necessary to (a) enforce the rights, claims and interests of the applicable trustee vis-a-vis any parties other than the Debtors, (b) allow each trustee to receive distributions under the Plan and to distribute them to the holders of the Cancelled Notes in accordance with the terms of the applicable indenture, (c) preserve any rights of the applicable trustee to compensation, reimbursement and indemnification under each of the applicable indentures solely as against any money or property distributable to holders of Cancelled Notes, (iv) permit each of the trustees to enforce any obligation owed to them under the Plan and (v) permit each of the trustees to appear in the Chapter 11 cases or in any proceeding in the Bankruptcy Court or any other court:


•	7.000% Senior Notes due 2019, issued pursuant to an indenture dated as of June 14, 2011, by and among Arch Coal, as issuer, UMB Bank National Association, as trustee, and the guarantors named therein, as amended, supplemented or revised thereafter;


•	7.250% Senior Notes due 2020, issued pursuant to an indenture dated as of August 9, 2010, by and among Arch Coal, as issuer, U.S. Bank National Association, as trustee, and the guarantors named therein, as amended, supplemented or revised thereafter;


•	7.250% Senior Notes due 2021, issued pursuant to an indenture dated as of June 14, 2011, by and among Arch Coal, as issuer, UMB Bank National Association, as trustee, and the guarantors named therein, as amended, supplemented or revised thereafter;


•	9.875% Senior Notes due 2019, issued pursuant to an indenture dated as of November 21, 2012, by and among Arch Coal, as issuer, UMB Bank National Association, as trustee, and the guarantors named therein, as amended, supplemented or revised thereafter; and


•	8.000% Second Lien notes due 2019, issued pursuant to an indenture dated as of December 17, 2013, by and among Arch Coal, as issuer, Wilmington Savings Fund Society, as trustee and collateral agent as successor to UMB Bank National Association, and the guarantors named therein, as amended, supplemented or revised thereafter.

On the Effective Date, by operation of the Plan, all outstanding obligations under the following credit agreement (the “Prepetition Credit Agreement”) entered into by Arch Coal and guaranteed by certain of Arch Coal’s subsidiaries and the related collateral, guaranty and other definitive agreements relating to the Prepetition Credit Agreement were cancelled and the Prepetition Credit Agreement was cancelled except as necessary to (i) enforce the rights, claims and interests of the Prepetition Agent (as defined below) and any predecessor thereof vis-a-vis the Lenders and any parties other than the Debtors, (ii) to allow the Prepetition Agent to receive distributions under the Plan and to distribute them to the lenders under the Prepetition Credit Agreement and (iii) preserve any rights of the Prepetition Agent and any predecessor thereof as against any money or property distributable to holders of claims arising out of the Prepetition Credit Agreement or any related transaction documents, including any priority in respect of payment and the right to exercise any charging lien:

•

Amended and Restated Credit Agreement, dated as of June 14, 2011 (as amended by the First Amendment, dated as of May 16, 2012, the Second Amendment, dated as of November 20, 2012, the Third Amendment, dated as of November 21, 2012 and the Fourth Amendment, dated as of December 17, 2013), among Arch Coal, Inc., as borrower, the lenders from time to time party thereto, Wilmington Trust, National Association, in its capacities as term loan facility administrative agent (as successor to Bank of America, N.A. in such capacity) and collateral agent (as successor to PNC Bank, National Association in such capacity) (in such capacities, the “Prepetition Agent”)

On the Effective Date, all outstanding obligations under the following credit agreement (the “DIP Credit Agreement”) other than contingent and/or unliquidated obligations were paid in cash in full, all commitments under the DIP Credit Agreement and the related transaction documents referred to therein as the “Loan Documents” were terminated, all liens on property of the Debtors arising out of or related to the DIP Facility terminated and the Loan Documents were cancelled except with respect to (a) contingent and and/or unliquidated obligations under the Loan Documents which survive the Effective Date and continue to be governed by the Loan Documents and (b) the relationships among the DIP Agent (as defined below) and the lenders under the DIP Credit Agreement, as applicable, including but not limited to, those provisions relating to the rights of the DIP Agent and the lenders to expense reimbursement, indemnification and other similar amounts, certain reinstatement obligations set forth in the DIP Credit Agreement and any provisions that may survive termination or maturity of the credit facility governed by the DIP Credit Agreement in accordance with the terms thereof:

•

Superpriority Secured Debtor-In-Possession Credit Agreement, dated as of January 21, 2016 (as amended by the Waiver and Consent and Amendment No. 1, dated as of March 4, 2016, Amendment No. 2, dated as of March 28, 2016, Amendment No. 3, dated as of April 26, 2016, Amendment No. 4, dated as of June 10, 2016, Amendment No. 5, dated as of June 23, 2016, Amendment No. 6, dated as of July 20, 2016, and Amendment No. 7, dated as of September 28, 2016) among Arch Coal, Inc., as borrower, certain subsidiaries of Arch Coal, Inc., as guarantors, the lenders from time to time party there and Wilmington Trust, National Association, in its capacity as administrative agent and as collateral agent (in such capacities, the “DIP Agent”).

Equity Securities

Under the Plan, 24,589,834 shares of Class A Common Stock and 410,166 shares of Class B Common Stock, par value $.01 per share, (“Class B Common Stock” and together with Class A Common Stock, “Common Stock”) were distributed to the secured lenders and to certain holders of general unsecured claims under the Plan on the Effective Date. In addition, on the Effective Date, Arch Coal issued Warrants to purchase up to an aggregate of 1,914,856 shares of Class A Common Stock. Arch Coal relied, based on the confirmation order it received from the Bankruptcy Court, on Section 1145(a)(1) of the U.S. Bankruptcy Code to exempt from the registration requirements of the Securities Act of 1933, as amended (i) the offer and sale of Common Stock to the secured lenders and to the general unsecured creditors, (ii) the offer and sale of the Warrants to the holders of claims arising under the Cancelled Notes and (iii) the offer and sale of the Class A Common Stock issuable upon exercise of the Warrants. Section 1145(a)(1) of the Bankruptcy Code exempts the offer and sale of securities under a plan of

reorganization from registration under Section 5 of the Securities Act and state laws if three principal requirements are satisfied:


•	the securities must be offered and sold under a plan of reorganization and must be securities of the debtor, of an affiliate participating in a joint plan of reorganization with the debtor or of a successor to the debtor under the plan of reorganization;


•	the recipients of the securities must hold claims against or interests in the debtor; and


•	the securities must be issued in exchange, or principally in exchange, for the recipient’s claim against or interest in the debtor.

Reorganization Value

Fresh start accounting provides, among other things, for a determination of the value to be assigned to the equity of the emerging company as of a date selected for financial reporting purposes. In conjunction with the bankruptcy proceedings, a third party financial advisor provided an enterprise value of the Company of approximately $650 million to $950 million. The final equity value of $687.5 million was based upon the approximate high end of the enterprise value established by the third party valuation plus excess cash of $64 million less the fair value of debt related to the New First Lien Debt Facility of $326.5 million. The high end of the enterprise value assumed a minimum cash balance at emergence of $250 million.

The enterprise value of the Company was estimated using various valuation methods including: (i) comparable public company analysis, (ii) discounted cash flow analysis (“DCF”) and (iii) sum-of-the-parts analysis. The comparable public company analysis is based on the enterprise value of selected publicly traded companies that have operating and financial characteristics comparable in certain respects to the Company, for example, operational requirements and risk and profitability characteristics. Selected companies are comprised of coal mining companies with primary operations in the United States. Under this methodology, certain financial multiples and ratios that measure financial performance and value are calculated for each selected company and then applied to the Company’s financials to imply an enterprise value for the Company.

The DCF analysis is a forward-looking enterprise valuation methodology that estimates the value of an assets or business by calculating the present value of expected future cash flows by that asset or business. The basis of the DCF analysis was the Company’s prepared projections which included a variety of estimates and assumptions, such as pricing and demand for coal. The Company’s pricing was based on its view of the market taking into account third party forward pricing curves adjusted for the quality of products sold by the Company. While the Company considers such estimates and assumptions reasonable, they are inherently subject to significant business, economic and competitive uncertainties, many of which are beyond the Company’s control and, therefore, may not be realized. Changes in these estimates and assumptions may have a significant effect on the determination of the Company’s enterprise value. The assumptions used in the calculations for the DCF analysis included projected revenue, cost and cash flows for the years ending December 31, 2016 through each respective mine life and represented the Company’s best estimates at the time the analysis was prepared. The DCF analysis was completed using discount rates at a range of estimated weighted average costs of capital ranging from 13.25% to 15.25% . The DCF analysis involves complex considerations and judgments concerning appropriate discount rates. Due to the unobservable inputs to the valuation, the fair value would be considered Level 3 in the fair value hierarchy.

The sum-of-the-parts analysis is a more detailed market multiples approach the values each part of a company’s business separately based upon the enterprise values of selected publicly traded companies that have operating and financial characteristics comparable in certain respects to each part of the reorganized Company. Under this methodology, certain financial multiples and ratios that measure financial performance and value are calculated for each selected comparable company and then applied to the relevant segment of the Company’s financials to imply an enterprise value for the Company.

Accounting Impact of Emergence

Upon emergence in accordance with ASC 852, the Company applied fresh start accounting to its consolidated financial statements as of October 1, 2016 because (i) the reorganization value of the assets of the emerging entity immediately before the date of confirmation was less than the total of all postpetition liabilities and allowed claims and (ii) the holders of the existing voting shares immediately before confirmation received less than 50 percent of the voting shares of the emerging entity. Upon adoption of fresh start accounting, the Company became a new entity for financial reporting purposes reflecting the Successor capital structure. As such, a new accounting basis in the identifiable assets and liabilities assumed was established with no retained earnings or accumulated other comprehensive income (loss) (“OCI”).

The following balance sheet illustrates the impacts of the implementation of the Plan and the application of fresh start accounting, which results in the opening balance sheet of the Successor company.



As of October 1, 2016 (In thousands)	Predecessor (a)			Effect of Plan (b)				Fresh Start Adjustments (c)				Successor
Assets
Current assets
Cash and cash equivalents	$	400,205		$	(199,718	)	(d)	$	—			$	200,487
Short term investments	111,451			—				—				111,451
Restricted cash	81,563			—				—				81,563
Trade accounts receivable	165,522			—				—				165,522
Other receivables	17,227			—				779			(j)	18,006
Inventories	159,410			—				(21,078		)	(k)	138,332
Prepaid royalties	4,805			—				—				4,805
Deferred income taxes	—			—				—				—
Coal derivative assets	2,180			—				—				2,180
Other current assets	36,960			6,367				53,851			(l)	97,178
Total current assets	979,323			(193,351		)		33,552				819,524

Property, plant and equipment, net	3,434,941			—				(2,363,829		)	(m)	1,071,112
Other assets
Prepaid royalties	20,997			—				(20,997		)	(n)	—
Equity investments	164,232			—				(61,606		)	(o)	102,626
Other noncurrent assets	58,569			34,495			(e)	37,503			(p)	130,567
Total other assets	243,798			34,495				(45,100		)		233,193
Total assets	$	4,658,062		$	(158,856	)		$	(2,375,377	)		$	2,123,829

Liabilities and Stockholders’ Equity (Deficit)
Liabilities not subject to compromise
Accounts payable	$	74,595		$	—			$	(250	)	(q)	$	74,345
Accrued expenses and other current liabilities	225,739			(36,331		)	(f)	26,644			(r)	216,052
Current maturities of debt	3,397			3,265			(g)	—				6,662
Total current liabilities	303,731			(33,066		)		26,394				297,059
Long-term debt	30,037			323,235			(g)	—				353,272
Asset retirement obligations	394,699			—				(60,570		)	(s)	334,129
Accrued pension benefits	23,716			—				24,565			(t)	48,281
Accrued other postretirement benefits	87,123			—				24,836			(t)	111,959
Accrued workers’ compensation	119,828			—				74,520			(u)	194,348
Deferred income taxes	—			—				—				—
Other noncurrent liabilities	96,410			—				888			(v)	97,298
Total liabilities not subject to compromise	1,055,544			290,169				90,633				1,436,346

Liabilities subject to compromise	5,278,612			(5,278,612		)	(h)	—				—

Total liabilities	6,334,156			(4,988,443		)		90,633				1,436,346

Stockholders’ equity (deficit)
Common stock, predecessor	2,145			(2,145		)	(i)	—				—
Common stock, successor	—			250			(b)	—				250
Paid-in capital, predecessor	3,056,307			(3,056,307		)	(i)	—				—
Paid-in capital, successor	—			687,233			(b)	—				687,233
Treasury stock, at cost	(53,863		)	53,863			(i)	—				—
Accumulated earnings (deficit)	(4,678,977		)	7,146,693			(i)	(2,467,716		)		—
Accumulated other comprehensive income (loss)	(1,706		)	—				1,706				—
Total stockholders’ equity (deficit)	(1,676,094		)	4,829,587				(2,466,010		)		687,483
Total liabilities and stockholders’ equity (deficit)	$	4,658,062		$	(158,856	)		$	(2,375,377	)		$	2,123,829


(a)	Represents the Predecessor consolidated balance sheet as of October 1, 2016.


(b)	Represents amounts recorded for the implementation of the Plan on the Effective Date. This includes the settlement of liabilities subject to compromise through a combination of cash payments, the issuance of new common stock and warrants and the issuance of new debt. The following is the calculation of the total pre-tax gain on the settlement of the liabilities subject to compromise:



	In thousands
Liabilities subject to compromise	$	5,278,612
Less amounts issued to settle claims:
Common stock (at par) Successor	(250		)
Warrants Successor	(14,822		)
Paid-in capital Successor	(672,411		)
Issuance of Term Loan Successor	(326,500		)
Cash payment to settle claims and professional fees	(122,525		)

Total pre-tax gain on plan effects	$	4,142,104


(c)	Represents the fresh start accounting adjustments required to record the assets and liabilities of the Company at fair value.


(d)	The following table reflects the use of cash at emergence:



	In thousands
Payment to secured lenders	$	43,496
Payments to unsecured creditors	42,399
Final adequate protection payment	36,331
Collateral requirements	31,665
Professional fees	31,630
Other	14,197

Total cash outflow at emergence	$	199,718


(e)	Represents amounts paid for required collateral deposits.


(f)	Represents the final adequate protection payments made to the secured lenders.


(g)	Represents the fair value of the $326.5 million new term loan of which $3.3 million is shown within current maturities of debt.


(h)	Liabilities subject to compromise include unsecured or under-secured liabilities incurred prior to the Chapter 11 filing; and consists of the following:



Previously Reported Balance Sheet Line	In thousands
Debt	$	5,026,806
Accrued expenses and other current liabilities	136,295
Accounts payable	106,297
Other noncurrent liabilities	9,214

Total liabilities subject to compromise	$	5,278,612


(i)	Reflects the impacts of the reorganization adjustments:



	In thousands
Total pre-tax gain on settlement of claims	$	4,142,104
Cancellation of predecessor common stock	2,145
Cancellation of predecessor paid-in capital	3,056,307
Cancellation of predecessor treasury stock	(53,863		)

Net impact on accumulated earnings (deficit)	$	7,146,693


(j)	Represents adjustments to record other receivables at fair value which includes an $0.8 million short-term receivable related to insurance coverage for self-insured workers’ compensation obligations.

(k)

Represents the following fair value adjustments: a $7.3 million increase related to coal inventory which was fair valued at estimated selling prices less the sum of selling costs, shipping costs and a reasonable profit allowance for the selling effort offset by a $28.4 million reduction in critical spare parts inventory. During fresh start accounting, the Company changed its accounting policy with respect to critical spare parts with long lead times; previously these items were valued within inventory, but prospectively, these items will be capitalized within property, plant and equipment when purchased and depreciated over the life of the related equipment.


(l)	Represents the short-term portion of above market coal sales contracts of $71.1 million offset by $11.3 million in reductions related to prepaid balances. The fair value of sales contracts was estimated using a discounted cash flow model and will be amortized into earnings as the coal is shipped throughout the term of the associated contracts.


(m)	Represents a $2.4 billion reduction in property, plant and equipment to estimated fair value as discussed below:



	Predecessor		Fresh Start Adjustments			Successor
(in thousands)
Net Coal Properties	$	2,358,779	$	(1,971,314	)	$	387,465
Net Plant & Equipment	812,888		(405,259		)	407,629
Net Deferred Charges	263,274		12,744			276,018

	$	3,434,941	$	(2,363,829	)	$	1,071,112

The fair value of coal properties was established at $387.5 million utilizing a discounted cash flow model and the market approach. The market approach was used to provide a starting value of the coal mineral reserves without consideration for economic obsolescence. The DCF model was based on assumptions market participants would use in the pricing of these assets as well as projections of revenues and expenditures that would be incurred to mine or maintain these coal reserves through the life of mine. The basis of the DCF analysis was the Company’s prepared projections which included a variety of estimates and assumptions, such as pricing and demand for coal. The Company’s pricing was based on its view of the market taking into account third party forward pricing curves adjusted for the quality of products sold by the Company.

The fair value of plant and equipment was set at $407.6 million utilizing both market and cost approaches. The market approach was used to estimate the value of assets where detailed information for the asset was available and an active market was identified with a sufficient number of sales of comparable property that could be independently verified through reliable sources. The cost approach was utilized where there were limitations in the secondary equipment market to derive values from. The first step in the cost approach is the estimation of the cost required to replace the asset via construction or purchasing a new asset with similar utility adjusting for depreciation due to physical deterioration, functional obsolescence due to technology changes and economic obsolescence due to external factors such as regulatory changes. Useful lives were assigned to all assets based on remaining future economic benefit of each asset.

The fair value of deferred charges represents the corresponding asset related to the asset retirement obligation discussed in item (q) below.


(n)	Represents a fair value adjustment to a long-term prepaid royalty balance that the Company has concluded should not be assigned value based on market conditions and after considering economic obsolescence.

(o)

Represents a fair value adjustment to the Company’s equity investments in Knight Hawk Holdings, LLC, a coal producer in the Illinois Basin; and Dominion Terminal Associates which operates a ground storage-to-vessel coal trans-loading facility in Newport News, Virginia. Equity investments were fair valued in a manner similar to the Company’s wholly-owned subsidiaries using a discounted cash flow model and comparable company approach. The discount rate selected was 14% and due to the unobservable nature of the inputs, the fair values are considered Level 3 in the fair value hierarchy.

(p)

Represents the long-term portion of above market coal sales contracts of $26.0 million and $18.6 million related to a long-term insurance receivable related to insurance coverage for self-insured workers’ compensation obligations partially offset by $13.2 million in reductions related to prepaid balances. The fair value of sales contracts was estimated using a discounted cash flow model and will be amortized into earnings as the coal is shipped throughout the term of the associated contracts.


(q)	Represents a fair value adjustment to miscellaneous accounts payable.

(r)

Represents fair value adjustments for the following: a $27.8 million increase related to the short-term portion of below market sales contracts offset by fair value adjustments to establish the current portion of pension, postretirement and workers’ compensation liabilities. The fair value of sales contracts was estimated using a discounted cash flow model and will be amortized into earnings as the coal is shipped throughout the term of the associated contracts.


(s)	Represents the fair value adjustment related to the Company’s asset retirement obligations which was calculated using discounted cash flow models based on current mine plans using the guidance provided within Accounting Standard Codification 410-20, “Asset Retirement Obligations.” The discount rates ranged from 7.06% to 9.08%.


(t)	Pension and postretirement benefits were fair valued based on plan assets and employee benefit obligations at October 1, 2016. The benefit obligations were computed using the applicable October 1, 2016 discount rates. In conjunction with fresh start accounting, the Company updated its mortality rate table assumptions and corridor assumption.

(u)

Represents fair value adjustments for workers’ compensation benefits, including occupational disease benefits, that were actuarially determined using the guidance provided within Accounting Standard Codification 712, “Non-retirement Post-employment Benefits.” Upon emergence, the Company’s accounting policy is to actuarially calculate this liability. Prior to emergence, the Company had accounted for its liability based on outstanding reserves calculated per third party administrators.

(v)

Represents the following fair value adjustments: $3.9 million increase related to the long-term portion of below market sales contracts partially offset by $3.1 million reduction in miscellaneous noncurrent liabilities. The fair value of sales contracts was estimated using a discounted cash flow model and will be amortized into earnings as the coal is shipped throughout the term of the associated contracts.

Reorganization Items, Net

In accordance with ASC 852, the statement of operations shall portray the results of operations of the reporting entity while it is in Chapter 11. Revenues, expenses (including professional fees), realized gains and losses, and provisions for losses resulting from reorganization and restructuring of the business shall be reported separately as reorganization items.

The Company’s reorganization items, net for the respective periods are as follows:



	Successor						Predecessor
	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016			Year Ended December 31, 2015
(In thousands)
Gain on settlement of claims (per above)	$	—		$	—		$	4,142,104		$	—
Fresh start adjustments, net (per above)	—			—			(2,466,010		)	—
Professional fees	(2,398		)	(759		)	(46,053		)	—

	$	(2,398	)	$	(759	)	$	1,630,041		$	—

Professional fees directly related to the reorganization include fees associated with advisors to the Company, certain secured creditors and the Creditors’ Committee. During the Successor period ended December 31, 2017, the Company continued to incur costs related to professional fees that are directly attributable to the reorganization.

Contractual Interest Expense During Bankruptcy

Upon the filing of bankruptcy, the Company discontinued recording interest expense on unsecured debt that was classified as a liability subject to compromise. Actual interest expense recorded on the Predecessor debt subsequent to the Petition Date was $135.9 million for the period January 1 through October 1, 2016; contractual interest during this time was $300.9 million.

Accumulated Other Comprehensive Income (Loss)

12 Months Ended

Dec. 31, 2017

Accumulated Other Comprehensive Income (Loss) [Abstract]

Accumulated Other Comprehensive Income (Loss)

The following items are included in accumulated other comprehensive income (loss):




				Pension,
				Postretirement						Accumulated
				and Other Post-						Other
	Derivative			Employment			Available-for-			Comprehensive
	Instruments			Benefits			Sale Securities			Income (Loss)
	(In thousands)
Predecessor Company
January 1, 2016	$	325		$	(721	)	$	(1,419	)	$	(1,815	)
Unrealized gains (losses)	(138		)	—			701			563
Amounts reclassified from accumulated other comprehensive income (loss)	(316		)	(1,363		)	1,225			(454		)
Fresh start accounting adjustment	129			2,084			(507		)	1,706
October 1, 2016	—			—			—			—
Successor Company
Unrealized gains (losses)	—			24,067			387			24,454
Amounts reclassified from accumulated other comprehensive income (loss)	—			—			—			—
December 31, 2016	$	—		$	24,067		$	387		$	24,454
Unrealized gains (losses)	497			(3,589		)	—			(3,092		)
Amounts reclassified from accumulated other comprehensive income (loss)	150			(758		)	(387		)	(995		)
December 31, 2017	$	647		$	19,720		$	—		$	20,367

The unrealized gain in the successor period ended December 31, 2016 is the result of changes in the discount rates used to calculate our pension, postretirement health and occupational disease obligations.

The following amounts were reclassified out of accumulated other comprehensive income (loss) during the respective periods:



Details about accumulated other comprehensive income components	Successor					Predecessor			Line Item in the Consolidated Statement of Operations
	Year Ended December 31, 2017			October 2 through December 31, 2016		January 1 through October 1, 2016
(in thousands)
Derivative instruments
Coal hedges	$	—		$	—	$	397		Revenues
Interest rate hedges	(150		)			—			Interest expense
	—			—		(81		)	Provision for (benefit from) income taxes
	$	(150	)	$	—	$	316		Net of tax

Pension, postretirement and other post-employment benefits
Amortization of prior service credits ¹	$	—		$	—	$	7,854
Amortization of net actuarial gains (losses) ¹	—			—		(6,010		)
Curtailments	(773		)	—		—
Settlements	1,531			—		—
	758			—		1,844			Total before tax
	—			—		(481		)	Provision for (benefit from) income taxes
	$	758		$	—	$	1,363		Net of tax

Available-for-sale securities ²	$	387		$	—	$	(2,263	)	Interest and investment income
	—			—		1,038			Provision for (benefit from) income taxes
	$	387		$	—	$	(1,225	)	Net of tax
¹ Production-related benefits and workers’ compensation costs are included in costs to produce coal.
² The gains and losses on sales of available-for-sale-securities are determined on a specific identification basis.

Divestitures (Notes)	12 Months Ended
Divestitures (Notes)	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Divestitures	Divestitures On September 14, 2017, the Company closed on its’ definitive agreement to sell Lone Mountain Processing LLC, an operating mine complex within the Company’s metallurgical coal segment, and two idled mining companies, Cumberland River Coal LLC and Powell Mountain Energy LLC to Revelation Energy LLC. The Company received $8.3 million of proceeds offset by $1.4 million in disbursements related to landholder consent fees and professional fees; and recorded a gain of $21.3 million which is reflected as a separate line, “Gain on sale of Lone Mountain Processing, Inc.,” within the Consolidated Statement of Operations. The gain included a $4.7 million curtailment gain related to black lung liabilities accrued for active employees at these operations. Losses from disposed operations resulting from Patriot Coal bankruptcy On December 31, 2005, Arch entered into a purchase and sale agreement with Magnum to sell certain operations. On July 23, 2008, Patriot acquired Magnum. On May 12, 2015, Patriot and certain of its wholly owned subsidiaries (“Debtors”), including Magnum, filed voluntary petitions for reorganization under Chapter 11 of the U.S. Code in the U.S. Bankruptcy Court for the Eastern District of Virginia. Subsequently, on October 28, 2015, Patriot’s Plan of Reorganization was approved, including an authorization to reject their collective bargaining agreements and modify certain union-related retiree benefits. As a result of the Plan of Reorganization, the Company became statutorily responsible for retiree medical benefits pursuant to Section 9711 of the Coal Industry Retiree Health Benefit Act of 1992 for certain retirees of Magnum who retired prior to October 1, 1994. In addition, the Company had provided surety bonds to Patriot related to permits that were sold to an affiliate of Virginia Conservation Legacy Fund, Inc. (“VCLF”). The Company recognized $116.3 million in losses in 2015 related to the previously disposed operations as a result of the Patriot Coal bankruptcy. On November 22, 2016, Arch entered into a”Collateral Use Agreement” which caused the replacement, substitution and discharge of reclamation surety bonds related to the former Magnum properties placed by Arch in exchange for a collateral release of $20 million held by the bonding company to VCLF.

Impairment Charges and Mine Closure Costs

12 Months Ended

Dec. 31, 2017

Impairment Charges and Mine Closure Costs [Abstract]

Impairment Charges and Mine Closure Costs

The following table summarizes the amounts reflected on the line “Asset impairment and mine closure costs” in the consolidated statements of operations:



	Successor				Predecessor
Description	Year Ended December 31, 2017		October 2 through December 31, 2016		January 1 through October 1, 2016		Year Ended December 31, 2015
(In thousands)
Coal lands and mineral rights	$	—	$	—	$	74,144	$	2,210,488
Plant and equipment	—		—		—		199,107
Deferred development	—		—		—		159,474
Prepaid royalties	—		—		3,406		41,990
Equity investments	—		—		40,920		21,325
Inventories	—		—		—		66
Other	—		—		10,797		(4,147		)
Total	$	—	$	—	$	129,267	$	2,628,303

January 1 Through October 1, 2016 Impairment Charges

During the period January 1 through October 1, 2016, the Company recorded the following to “Asset impairment and mine closure costs” in the Consolidated Statements of Operations: $74.1 million recorded in the first quarter related to the impairment of coal reserves and surface land in Kentucky that are being leased to a mining company that idled its mining operations; $3.4 million recorded in the first quarter related to the impairment on the portion of an advance royalty balance on a reserve base mined at the Company’s Mountain Laurel operation that will not be recouped; $2.9 million recorded in the first quarter related to an other-than-temporary-impairment charge on an available-for-sale security; a $38.0 million impairment recorded in the second quarter related to the Company’s equity investment in a brownfield bulk commodity terminal on the Columbia River in Longview, Washington as the Company relinquished its ownership rights in exchange for future throughput rights; $7.2 million of severance expense related to headcount reductions during the first half of the year; a $3.6 million curtailment charge related to the Company’s pension, postretirement health and black lung actuarial liabilities due to headcount reductions in the first half of the year.

2015 Impairment Charges

In 2015, as a result of the continued deterioration in thermal and metallurgical coal markets and projections for a muted pricing recovery, certain of the Company’s mine complexes have incurred and are expected to continue to incur operating losses. The Company determined that the further weakening of the pricing environment in the last half of the year and the projected operating losses represented indicators of impairment with respect to certain of its long-lived assets or assets groups. Using current pricing expectations which reflected marketplace participant assumptions, life of mine cash flows were used to determine if the undiscounted cash flows exceeded the current asset values for certain operating complexes in the Company’s Appalachia segment. For multiple operating complexes, the undiscounted cash flows did not exceed the carrying value of the long-lived assets. Discounted cash flows were utilized to reduce the carrying value of those assets to fair value. The discount rate used reflected the then current financial difficulties present in the commodities sector in general and coal mining specifically; the perceived risk of financing coal mining in light of industry defaults; and the lack of an active market for buying or selling coal mining assets. Additionally, the Company determined that the then current market conditions represented an indicator of impairment for certain undeveloped coal properties that were acquired in times of significantly higher coal prices. The then current prices and the significant capital outlay that would have been required to develop these reserves indicated that the carrying value was not recoverable. As a result the Company recorded a $2.6 billion asset impairment charge in the last two quarters of 2015 of which $2.1 billion was recorded during the third quarter and the remaining $0.5 billion was recorded in the fourth quarter. Of the total charge. $2.2 billion was recorded to the Company’s Appalachia segment, with the remaining $0.4 billion recorded to the Company’s Other operating segment. There is no fair value remaining related to the impaired assets.

During the second quarter of 2015, the Company recorded $19.1 million to “Asset impairment and mine closure costs” in the Consolidated Statements of Operations. An impairment charge of $12.2 million related to the portion of an advance royalty balance on a reserve base mined at the Company’s Mountain Laurel, Spruce and Briar Branch operations that was determined would not be recouped based on estimates of sales volume and pricing through the March 2017 recoupment period. Additionally, the Company recorded a $5.6 million impairment charge related to the closure of a higher-cost mining complex serving the metallurgical coal markets.

Losses from disposed operations resulting from Patriot Coal Bankruptcy	12 Months Ended
	Dec. 31, 2017
Discontinued Operations and Disposal Groups [Abstract]
Losses from disposed operations resulting from Patriot Coal Bankruptcy	Divestitures On September 14, 2017, the Company closed on its’ definitive agreement to sell Lone Mountain Processing LLC, an operating mine complex within the Company’s metallurgical coal segment, and two idled mining companies, Cumberland River Coal LLC and Powell Mountain Energy LLC to Revelation Energy LLC. The Company received $8.3 million of proceeds offset by $1.4 million in disbursements related to landholder consent fees and professional fees; and recorded a gain of $21.3 million which is reflected as a separate line, “Gain on sale of Lone Mountain Processing, Inc.,” within the Consolidated Statement of Operations. The gain included a $4.7 million curtailment gain related to black lung liabilities accrued for active employees at these operations. Losses from disposed operations resulting from Patriot Coal bankruptcy On December 31, 2005, Arch entered into a purchase and sale agreement with Magnum to sell certain operations. On July 23, 2008, Patriot acquired Magnum. On May 12, 2015, Patriot and certain of its wholly owned subsidiaries (“Debtors”), including Magnum, filed voluntary petitions for reorganization under Chapter 11 of the U.S. Code in the U.S. Bankruptcy Court for the Eastern District of Virginia. Subsequently, on October 28, 2015, Patriot’s Plan of Reorganization was approved, including an authorization to reject their collective bargaining agreements and modify certain union-related retiree benefits. As a result of the Plan of Reorganization, the Company became statutorily responsible for retiree medical benefits pursuant to Section 9711 of the Coal Industry Retiree Health Benefit Act of 1992 for certain retirees of Magnum who retired prior to October 1, 1994. In addition, the Company had provided surety bonds to Patriot related to permits that were sold to an affiliate of Virginia Conservation Legacy Fund, Inc. (“VCLF”). The Company recognized $116.3 million in losses in 2015 related to the previously disposed operations as a result of the Patriot Coal bankruptcy. On November 22, 2016, Arch entered into a”Collateral Use Agreement” which caused the replacement, substitution and discharge of reclamation surety bonds related to the former Magnum properties placed by Arch in exchange for a collateral release of $20 million held by the bonding company to VCLF.

Inventories

12 Months Ended

Dec. 31, 2017

Inventory Disclosure [Abstract]

Inventories

Inventories consist of the following:



	December 31, 2017		December 31, 2016
(In thousands)
Coal	$	54,692	$	37,268
Repair parts and supplies	74,268		76,194
	$	128,960	$	113,462

The repair parts and supplies are stated net of an allowance for slow-moving and obsolete inventories of $0.3 million at December 31, 2017 and $0.0 million at December 31, 2016.

Investments in Available-for-Sale Securities

12 Months Ended

Dec. 31, 2017

Available-for-sale Securities [Abstract]

Investments in Available-for-Sale Securities

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

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



	December 31, 2017
										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	$	64,151	$	22	$	(73	)	$	64,100	$	64,100	$	—
Corporate notes and bonds	92,038		—		(292		)	91,746		91,746		—
Total Investments	$	156,189	$	22	$	(365	)	$	155,846	$	155,846	$	—



	December 31, 2016
										Balance Sheet
			Gross		Gross					Classification
			Unrealized		Unrealized			Fair		Short-Term		Other
	Cost Basis		Gains		Losses			Value		Investments		Assets
	(In thousands)
Available-for-sale:
Corporate notes and bonds	$	88,161	$	—	$	(89	)	$	88,072	$	88,072	$	—
Equity securities	1,749		388		—			2,137		—		2,137
Total Investments	$	89,910	$	388	$	(89	)	$	90,209	$	88,072	$	2,137

The aggregate fair value of investments with unrealized losses that had been owned for less than a year was $132.0 million and $47.6 million at December 31, 2017 and 2016, respectively. The aggregate fair value of investments with unrealized losses that have been owned for over a year was $0.0 million and $40.4 million at December 31, 2017 and 2016, respectively.

The debt securities outstanding at December 31, 2017 have maturity dates ranging from the first quarter of 2018

through the second quarter of 2019. 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, if needed.

Equity Method Investments and Membership Interests in Joint Ventures

12 Months Ended

Dec. 31, 2017

Equity Method Investments and Joint Ventures [Abstract]

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. 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.

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



(In thousands)	Knight Hawk			DTA			Millennium			Tongue River			Other			Total
Predecessor Company
January 1, 2015	$	158,477		$	13,738		$	40,223		$	20,740		$	2,664		$	235,842
Advances to (distributions from) affiliates, net	(29,862		)	3,207			7,052			913			330			(18,360		)
Equity in comprehensive income (loss)	22,977			(3,706		)	(9,686		)	(328		)	(1,278		)	7,979
Impairment of equity investment	—			—			—			(21,325		)	—			(21,325		)
Sale of equity investment	—			—			—			—			(2,259		)	(2,259		)
December 31, 2015	151,592			13,239			37,589			—			(543		)	201,877
Advances to (distributions from) affiliates, net	(8,374		)	1,474			1,966			—			—			(4,934		)
Equity in comprehensive income (loss)	9,033			(2,095		)	(1,530		)	—			(94		)	5,314
Impairment of equity investment	—			—			(38,025		)	—			—			(38,025		)
Fresh start accounting adjustment	(58,251		)	(4,018		)	—			—			662			(61,607		)
October 1, 2016	94,000			8,600			—			—			25			102,625
Successor Company
Advances to (distributions from) affiliates, net	(9,076		)	822			—			—			—			(8,254		)
Equity in comprehensive income (loss)	2,569			(841		)	—			—			(25		)	1,703
December 31, 2016	$	87,493		$	8,581		$	—		$	—		$	—		$	96,074
Investments in affiliates	—			7,158			—			—			—			7,158
Advances to (distributions from) affiliates, net	(8,736		)	3,014			—			—			—			(5,722		)
Equity in comprehensive income (loss)	11,409			(2,812		)	—			—			—			8,597

December 31, 2017	$	90,166		$	15,941		$	—		$	—		$	—		$	106,107

The Company holds a 49% equity interest in Knight Hawk Holdings, LLC (“Knight Hawk”), a coal producer in the Illinois Basin.

The Company holds a general partnership interest in Dominion Terminal Associates (“DTA”), which is accounted for under the equity method. In March 2017, the Company paid $7.2 million through an auction process held by one of the existing owners, increasing its ownership in DTA from 21.875% to 35%. DTA operates a ground storage-to-vessel coal transloading facility in Newport News, Virginia for use by the partners. Under the terms of a throughput and handling agreement with DTA, each partner is charged its share of cash operating and debt-service costs in exchange for the right to use the facility’s loading capacity and is required to make periodic cash advances to DTA to fund such costs.

The Company previously held a 38% ownership interest in Millennium Bulk Terminals-Longview, LLC (“Millennium”), the owner of a brownfield bulk commodity terminal on the Columbia River near Longview, Washington. Millennium continues to work on obtaining the required approvals and necessary permits to complete dredging and other upgrades to ship coal, alumina and cementitious material from the terminal. During the second quarter of 2016, the Company recorded an impairment charge of $38.0 million representing the entire value of its equity investment as the Company relinquished its ownership rights in exchange for future throughput rights through the facility when completed.

The Company previously held a 35% membership interest in the Tongue River Holding Company, LLC (“Tongue River”) joint venture. Tongue River was formed to develop and construct a railway line near Miles City, Montana and the Otter Creek reserves formerly controlled by the Company. The Company had the right, upon the receipt of permits and approval for construction or under other prescribed circumstances, to require the other investors to purchase all of the Company’s units in the venture at an amount equal to the capital contributions made by the Company at that time, less any distributions received. During the third quarter of 2015, the Company recorded an impairment charge of $21.3 million representing the entire value of the Company’s investment in the project; the impairment charge is included on the line “Asset impairment and mine closure costs.”

The Company is not required to make any future contingent payments related to development financing for any of its equity investees.

Sales Contracts

12 Months Ended

Dec. 31, 2017

Acquired Sales Contracts [Abstract]

Sales Contracts

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



	December 31, 2017								December 31, 2016
	Assets			Liabilities			Net Total		Assets			Liabilities			Net Total
	(In thousands)								(In thousands)
Original fair value	$	97,196		$	31,742				$	97,196		$	31,742
Accumulated amortization	(84,760		)	(29,979		)			(25,625		)	(24,829		)
Total	$	12,436		$	1,763		$	10,673	$	71,571		$	6,913		$	64,658
Balance Sheet classification:
Other current	$	12,432		$	934				$	59,702		$	5,114
Other noncurrent	$	4		$	829				$	11,869		$	1,799

The Company anticipates the majority of the remaining net book value of sales contracts to be amortized in 2018 based upon expected shipments.

Derivatives

12 Months Ended

Dec. 31, 2017

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivatives

Interest rate risk management

The Company has entered into some interest rate swaps to reduce the variability of cash outflows associated with interest payments on its variable rate term loan. These swaps have been designated as cash flow hedges. For additional information on these arrangements, see Note 14, “Debt and Financing Arrangements” in the Consolidated Financial Statements.

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 42 to 46 million gallons of diesel fuel for use in its operations during 2018. 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 December 31, 2017, the Company had heating oil call options for approximately 26.2 million gallons at an average strike price of $1.84.

Coal risk management positions

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

At December 31, 2017, the Company held derivatives for risk management purposes that are expected to settle in the following years:



(Tons in thousands)	2018	2019	Total
Coal sales	1,706	159	1,865
Coal purchases	747	—	747

The Company may also enter into natural gas options to protect the Company from decreases in natural gas prices, which could impact thermal coal demand. These options are not designated as hedges. Additionally, the Company may enter into nominal quantities of foreign currency options protecting for decreases in the Australian to United States dollar exchange rate, which could impact metallurgical coal demand. These options are not designated as hedges.

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 unrecognized losses of $1.2 million in the trading portfolio are expected to be realized in 2018.

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 consolidated balance sheets. The amounts shown in the table below represent the fair value position of individual contracts, and not the net position presented in the accompanying consolidated balance sheets.

The fair value and location of derivatives reflected in the accompanying consolidated balance sheets are as follows:



	December 31, 2017									December 31, 2016
Fair Value of Derivatives	Asset			Liability						Asset			Liability
(In thousands)	Derivative			Derivative						Derivative			Derivative
Derivatives Designated as Hedging Instruments
Coal	$	942		$	(2,146	)				$	—		$	(15	)

Derivatives Not Designated as Hedging Instruments
Heating oil -- diesel purchases	5,354			—						4,646			—
Coal held for trading purposes, exchange traded swaps and futures	44,088			(45,221		)				68,948			(68,740		)
Coal -- risk management	5,139			(9,892		)				475			(580		)
Natural gas	27			—						86			(13		)
Total	54,608			(55,113		)				74,155			(69,333		)
Total derivatives	55,550			(57,259		)				74,155			(69,348		)
Effect of counterparty netting	(50,042		)	50,042						(69,247		)	69,247
Net derivatives as classified in the balance sheets	$	5,508		$	(7,217	)	$	(1,709	)	$	4,908		$	(101	)	$	4,807



		December 31, 2017			December 31, 2016
Net derivatives as reflected on the balance sheets
Heating oil	Other current assets	$	5,354		$	4,646
Coal	Other current assets	154			262
	Accrued expenses and other current liabilities	(7,217		)	(101		)
		$	(1,709	)	$	4,807

The Company had a current asset for the right to reclaim cash collateral of $16.2 million and $2.8 million at December 31, 2017 and 2016, respectively. These amounts are not included with the derivatives presented in the table above and are included in “other current assets” in the accompanying consolidated balance sheets.

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

Derivatives used in Cash Flow Hedging Relationships (in thousands)

For the noted periods,



		Gain (Loss) Recognized in Other Comprehensive Income (Effective Portion)
		Successor					Predecessor
		Year Ended December 31, 2017			October 2 through December 31, 2016		January 1 through October 1, 2016			Year Ended December 31, 2015
Coal sales	⁽¹⁾	$	(2,127	)	$	—	$	(672	)	12,816
Coal purchases	⁽²⁾	942			—		536			(6,718		)
		$	(1,185	)	$	—	$	(136	)	$	6,098


		Gains (Losses) Reclassified from Other Comprehensive Income into Income (Effective Portion)
		Successor					Predecessor
		Year Ended December 31, 2017			October 2 through December 31, 2016		January 1 through October 1, 2016			Year Ended December 31, 2015
Coal sales		$	—		$	—	$	1,634		$	18,635
Coal purchases		—			—		(1,237		)	(9,060		)
		$	—		$	—	$	397		$	9,575

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 respective periods.

Derivatives Not Designated as Hedging Instruments (in thousands)

For the noted periods,



		Gain (Loss) Recognized
		Successor						Predecessor
		Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016			Year Ended December 31, 2015
Coal — unrealized	⁽³⁾	$	(4,648	)	$	(408	)	$	(1,662	)	$	(3,883	)
Coal — realized	⁽⁴⁾	$	—		$	116		$	(476	)	$	3,236
Heating oil — diesel purchases	⁽⁴⁾	$	(1,057	)	$	827		$	826		$	(8,294	)
Natural gas		$	(774	)	$	(91	)	$	(463	)	$	878
Foreign currency		$	—		$	(9	)	$	(451	)	$	(867	)

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 losses of $2.0 million for the year ended December 31, 2017; an immaterial amount for the period October 2 through December 31, 2016; net unrealized and realized losses of $0.9 million for the period January 1 through October 1, 2016; and net unrealized and realized gains of $5.7 million during the year ended December 31, 2015, respectively, related to its trading portfolio, which are included in the caption “Change in fair value of coal derivatives and coal trading activities, net” in the accompanying consolidated statements of operations, and are not included in the previous tables reflecting the effects of derivatives on measures of financial performance.

Based on fair values at December 31, 2017, amounts on derivative contracts designated as hedge instruments in cash flow hedges expected to be reclassified from other comprehensive income into earnings during the next twelve months are losses of $1.2 million.

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2017

Accrued Expenses and Other Current Liabilities [Abstract]

Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following:



	December 31, 2017		December 31, 2016
(In thousands)
Payroll and employee benefits	$	53,149	$	58,468
Taxes other than income taxes	77,017		92,733
Interest	246		8,032
Sales contracts	934		5,114
Workers’ compensation	18,782		15,184
Asset retirement obligations	19,840		19,515
Other	14,193		6,194
	$	184,161	$	205,240

Debt and Financing Arrangements

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Debt and Financing Arrangements



	December 31, 2017			December 31, 2016
(In thousands)
Term loan due 2024 ($297.8 million face value)	$	296,435		$	—
Term loan due 2021 ($325.7 million face value)	$	—		$	325,684
Other	36,514			37,195
Debt issuance costs	(7,032		)	—
	325,917			362,879
Less current maturities of debt	15,783			11,038
Long-term debt	$	310,134		$	351,841

Term Loan Facility

On March 7, 2017, the Company entered into a new senior secured term loan credit agreement in an aggregate principal amount of $300 million (the “New Term Loan Debt Facility”) with Credit Suisse AG, Cayman Islands Branch, as administrative agent and collateral agent (in such capacities, the “Agent”), and the other financial institutions from time to time party thereto (collectively, the “Lenders”). The New Term Loan Debt Facility was issued at 99.50% of the face amount and will mature on March 7, 2024.

On September 25, 2017, the Company entered into the First Amendment (the “Amendment”) to its Credit Agreement, dated as of March 7, 2017, among Arch Coal as borrower, the lenders from time to time party thereto, and Credit Suisse AG, Cayman Islands Branch, as administrative agent and collateral agent.

The Amendment reduces the interest rate on the $300 million term loan facility to, at the option of Arch Coal, either (i) the London interbank offered rate (“LIBOR”) plus an applicable margin of 3.25%, subject to a 1.00% LIBOR floor, or (ii) a base rate plus an applicable margin of 2.25%. The Amendment also resets the 1.00% call premium to apply to repricing events that occur on or prior to March 26, 2018.

Borrowings under the New Term Loan Debt Facility bear interest at a per annum rate equal to, at the Company’s option, either (i) a London interbank offered rate plus an applicable margin of 4%, subject to a 1% LIBOR floor (the “LIBOR Rate”), or (ii) a base rate plus an applicable margin of 3%. The term loans provided under the New Term Loan Debt Facility (the “Term Loans”) are subject to quarterly principal amortization payments in an amount equal to $750,000.

The New Term Loan Debt Facility is guaranteed by all existing and future wholly owned domestic subsidiaries of the Company (collectively, the “Subsidiary Guarantors” and, together with Arch Coal, the “Loan Parties”), subject to customary exceptions, and is secured by first priority security interests on substantially all assets of the Loan Parties, including 100% of the voting equity interests of directly owned domestic subsidiaries and 65% of the voting equity interests of directly owned foreign subsidiaries, subject to customary exceptions.

The Company has the right to prepay Term Loans at any time and from time to time in whole or in part without premium or penalty, upon written notice, except that any prepayment of Term Loans that bear interest at the LIBOR Rate other than at the end of the applicable interest periods therefor shall be made with reimbursement for any funding losses and redeployment costs of the Lenders resulting therefrom.

The New Term Loan Debt Facility is subject to certain usual and customary mandatory prepayment events, including 100% of net cash proceeds of (i) debt issuances (other than debt permitted to be incurred under the terms of the New Term Loan Debt Facility) and (ii) non-ordinary course asset sales or dispositions, subject to customary thresholds, exceptions and reinvestment rights.

The New Term Loan Debt Facility contains customary affirmative covenants and representations.

The New Term Loan Debt Facility also contains customary negative covenants, which, among other things, and subject to certain exceptions, include restrictions on (i) indebtedness, (ii) liens, (iii) liquidations, mergers, consolidations and acquisitions, (iv) disposition of assets or subsidiaries, (v) affiliate transactions, (vi) creation or ownership of certain subsidiaries, partnerships and joint ventures, (vii) continuation of or change in business, (viii) restricted payments, (ix) prepayment of subordinated and junior lien indebtedness, (x) restrictions in agreements on dividends, intercompany loans and granting liens on the collateral, (xi) loans and investments, (xii) sale and leaseback transactions, (xiii) changes in organizational documents and fiscal year and (xiv) transactions with respect to bonding subsidiaries. The New Term Loan Debt Facility does not contain any financial maintenance covenant.

The New Term Loan Debt Facility contains customary events of default, subject to customary thresholds and exceptions, including, among other things, (i) nonpayment of principal and nonpayment of interest and fees, (ii) a material inaccuracy of a representation or warranty at the time made, (iii) a failure to comply with any covenant, subject to customary grace periods in the case of certain affirmative covenants, (iv) cross-events of default to indebtedness of at least $50 million, (v) cross-events of default to surety, reclamation or similar bonds securing obligations with an aggregate face amount of at least $50 million, (vi) uninsured judgments in excess of $50 million, (vii) any loan document shall cease to be a legal, valid and binding agreement, (viii) uninsured losses or proceedings against assets with a value in excess of $50 million, (ix) certain ERISA events, (x) a change of control or (xi) bankruptcy or insolvency proceedings relating to the Company or any material subsidiary of the Company.

On the effective date of the New Term Loan Debt Facility, all outstanding obligations under the Company’s previously existing term loan credit agreement, dated as of October 5, 2016, among the Company, as borrower, the lender party thereto and Wilmington Trust, National Association, as administrative agent and collateral agent (the “Previous First Lien Debt Facility”), other than indemnification and other contingent obligations, were paid in cash in full and the related transaction documents were terminated (other than with respect to certain provisions that customarily survive termination); there was no gain or loss recognized on the extinguishment of the previously existing term loan credit agreement. All liens on property of the Company and the guarantors thereunder arising out of or related to the Previous First Lien Debt Facility were terminated.

Accounts Receivable Securitization Facility

On April 27, 2017, the Company extended and amended its existing trade accounts receivable securitization facility provided to Arch Receivable Company, LLC, a special-purpose entity that is a wholly owned subsidiary of the Company (“Arch Receivable”) (the “Extended Securitization Facility”), which supports the issuance of letters of credit and requests for cash advances. The amendment to the Extended Securitization Facility decreases the borrowing capacity from $200 million to $160 million and extends the maturity date to the date that is three years after the Securitization Facility Closing Date. Pursuant to the Extended Securitization Facility, Arch Receivable also agreed to a revised schedule of fees payable to the administrator and the providers of the Extended Securitization Facility.

The Extended Securitization Facility will terminate at the earliest of (i) three years from the Securitization Facility Closing Date, (ii) if the Liquidity (defined in the Extended Securitization Facility and consistent with the definition in the New Inventory Facility) is less than $175 million for a period of 60 consecutive days, the date that is the 364th day after the first day of such 60 consecutive day period and (iii) the occurrence of certain predefined events substantially consistent with the existing transaction documents. Under the Extended Securitization Facility, Arch Receivable, the Company and certain of its subsidiaries party to the Extended Securitization Facility have granted to the administrator of the Extended Securitization Facility a first priority security interest in eligible trade accounts receivable generated by such parties from the sale of coal and all proceeds thereof. As of December 31, 2017, letters of credit totaling $85.0 million were outstanding under the facility with no additional availability for borrowings.

Inventory-Based Revolving Credit Facility

On April 27, 2017, the Company and certain subsidiaries of Arch Coal entered into a new senior secured inventory-based revolving credit facility in an aggregate principal amount of $40 million (the “New Inventory Facility”) with Regions Bank (“Regions”) as administrative agent and collateral agent (in such capacities, the “Agent”), as lender and swingline lender (in such capacities, the “ Lender ”) and as letter of credit issuer. Availability under the New Inventory Facility is subject to a borrowing base consisting of (i) 85% of the net orderly liquidation value of eligible coal inventory, (ii) the lesser of (x) 85% of the net orderly liquidation value of eligible parts and supplies inventory and (y) 35% of the amount determined pursuant to clause (i), and (iii) 100% of Arch Coal’s Eligible Cash (defined in the New Inventory Facility), subject to reduction for reserves imposed by Regions.

The commitments under the New Inventory Facility will terminate on the date that is the earliest to occur of (i) the third anniversary of the Inventory Facility Closing Date, (ii) the date, if any, that is 364 days following the first day that Liquidity (defined in the New Inventory Facility and consistent with the definition in the Extended Securitization Facility (as defined below)) is less than $250 million for a period of 60 consecutive days and (iii) the date, if any, that is 60 days following the maturity, termination or repayment in full of the Extended Securitization Facility.

Revolving loan borrowings under the New Inventory Facility bear interest at a per annum rate equal to, at the option of the Company, either at the base rate or the London interbank offered rate plus, in each case, a margin ranging from 2.25% to 2.50% (in the case of LIBOR loans) and 1.25% to 1.50% (in the case of base rate loans) determined using a Liquidity-based grid. Letters of credit under the New Inventory Facility are subject to a fee in an amount equal to the applicable margin for LIBOR loans, plus customary fronting and issuance fees.

All existing and future direct and indirect domestic subsidiaries of the Company, subject to customary exceptions, will either constitute co-borrowers under or guarantors of the New Inventory Facility (collectively with the Company, the “Loan Parties”). The New Inventory Facility is secured by first priority security interests in the ABL Priority Collateral (defined in the New Inventory Facility) of the Loan Parties and second priority security interests in substantially all other assets of the Loan Parties, subject to customary exceptions (including an exception for the collateral that secures the Extended Securitization Facility).

The Company has the right to prepay borrowings under the New Inventory Facility at any time and from time to time in whole or in part without premium or penalty, upon written notice, except that any prepayment of such borrowings that bear interest at the LIBOR rate other than at the end of the applicable interest periods therefore shall be made with reimbursement for any funding losses and redeployment costs of the Lender resulting therefrom.

The New Inventory Facility is subject to certain usual and customary mandatory prepayment events, including non-ordinary course asset sales or dispositions, subject to customary thresholds, exceptions (including exceptions for required prepayments under the Company’s term loan facility) and reinvestment rights.

The New Inventory Facility contains certain customary affirmative and negative covenants; events of default, subject to customary thresholds and exceptions; and representations, including certain cash management and reporting requirements that are customary for asset-based credit facilities. The New Inventory Facility also includes a requirement to maintain Liquidity equal to or exceeding $175 million at all times. As of December 31, 2017, letters of credit totaling $29.0 million were outstanding under the facility with $1.1 million additional availability for borrowings.

Interest Rate Swaps

During the second quarter of 2017, the Company entered into a series of interest rate swaps to fix a portion of the LIBOR interest payments due under the term loan. The interest rate swaps qualify for cash flow hedge accounting treatment and as such, the change in the fair value of the interest rate swaps are recorded on the Company’s Consolidated Balance Sheet as an asset or liability with the effective portion of the gains or losses reported as a component of accumulated other comprehensive income and the ineffective portion reported in earnings. As interest payments are made on the term loan, amounts in accumulated other comprehensive income will be reclassified into earnings through interest expense to reflect a net interest on the term loan equal to the effective yield of the fixed rate of the swap plus 3.25% which is the spread on the revised LIBOR term loan. In the event that an interest rate swap is terminated prior to maturity, gains or losses in accumulated other comprehensive income will remain deferred and reclassified into earnings in the periods which the hedged forecasted transaction affects earnings.

Below is a summary of the Company’s outstanding interest rate swap agreements designated as hedges as of

December 31, 2017:



Notional Amount (in millions)	Effective Date	Fixed Rate	Receive Rate	Expiration Date

$250.0	June 30, 2017	1.372%	1-month LIBOR	June 29, 2018
$250.0	June 29, 2018	1.662%	1-month LIBOR	June 28, 2019
$200.0	June 28, 2019	1.952%	1-month LIBOR	June 30, 2020
$150.0	June 30, 2020	2.182%	1-month LIBOR	June 30, 2021

The fair value of the interest rate swaps at December 31, 2017 is an asset of $1.8 million which is recorded within Other noncurrent assets with the offset to accumulated other comprehensive income on the Company’s Consolidated Balance Sheet. The Company realized $0.1 million of losses during the year ended December 31, 2017 related to settlements of the interest rate swaps which was recorded to interest expense on the Company’s Consolidated Statement of Operations. The interest rate swaps are classified as level 2 within the fair value hierarchy.

Debt Maturities

The contractual maturities of debt as of December 31, 2017 are as follows:



Year	(In thousands)
2018	$	16,809
2019	11,119
2020	11,442
2021	8,853
2022	3,130
Thereafter	282,911
	$	334,264

Financing Costs

The Company paid financing costs of $10.1 million during the year ended December 31, 2017; zero during the period October 2 through December 31, 2016; $23.0 million during the period January 1 through October 1, 2016; and zero during the year ended December 31, 2015, respectively, in conjunction with its financing activities.

The Company incurred $2.5 million and $2.2 million of legal fees and financial advisory fees associated with debt restructuring activities during the period ended December 31, 2017 and January 1 through October 1, 2016, respectively. Additionally, the Company incurred $24.2 million of legal fees and financial advisory fees associated with debt restructuring activities during 2015. During the year ended December 31, 2015 the Company wrote off $3.7 million of deferred financing costs related to the termination of the revolver facility. All amounts have been reflected in the line, “Net loss resulting from early retirement and refinancing of debt” in the Consolidated Statement of Operations.

Taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Taxes

In 2016, under the Plan of bankruptcy reorganization, the Company’s pre-petition equity, bank related debt and certain other obligations were cancelled and extinguished. Absent an exception, a debtor recognizes cancellation of debt income (CODI) upon discharge of its outstanding indebtedness for an amount of consideration that is less than its adjusted issue price. In accordance with Internal Revenue Code (IRC) Section 108, the Company excluded the amount of discharged indebtedness from taxable income since the IRC provides that a debtor in a bankruptcy case may exclude CODI from income but must reduce certain tax attributes by the amount of CODI realized as a result of the consummation of a plan of reorganization. The amount of CODI realized by a taxpayer is the adjusted issue price of any indebtedness discharged less than the sum of (i) the amount of cash paid, (ii) the issue price of any new indebtedness issued, and (iii) the fair market value of any other consideration, including equity, issued.

CODI from the discharge of indebtedness was $3,414 million. As a result of the CODI and in accordance with IRC rules, the Company reduced its gross federal net operating loss (NOL) carryovers $3,185 million and its alternative minimum tax (AMT) credits $76 million. The Company was able to retain $957.1 million of gross federal NOLs, $25.6 million of AMT credit and $64.5 million of capital loss carryforwards following the bankruptcy.

Due to changes in ownership that occurred in connection with the Company’s emergence from bankruptcy, there was a change in ownership for purposes of IRC Section 382. Section 382 provides a combined annual limitation with respect to the ability of a corporation to use its NOLs, AMT credits and capital loss carryforwards generated before the ownership change against future taxable income. The Company’s annual limit under IRC section 382 is estimated to be $29.8 million. The Company had a net unrealized built-in gain, based on comparing the fair value and carryover tax basis in assets, at the time of the ownership change, therefore, certain built-in gains recognized within five years after the ownership change will increase the annual IRC section 382 limit for the five year recognition period beginning October 1, 2016 through September 30, 2021. There is uncertainty surrounding which assets with built-in gain will be realized within the five year period following the Company’s emergence from bankruptcy and allow the Company to realize the incremental net operating losses and credit in excess of the base 382 limitation. The Company is reflecting a deferred tax asset for the full amount of the net operating losses and credit carryforwards. If at some point in time it becomes evident that some portion of the deferred tax assets will not be realizable, the deferred tax asset, and offsetting valuation allowance will be reduced.

The Company is subject to U.S. federal income tax as well as income tax in multiple state jurisdictions. The tax years 2002 through 2017 remain open to examination for U.S. federal income tax matters and 2002 through 2017 remain open to examination for various state income tax matters.

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



	Successor						Predecessor
	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016			Year Ended December 31, 2015
(In thousands)
Current:
Federal	$	835		$	—		$	—		$	—
State	31			(252		)	7			3
Total current	866			(252		)	7			3
Deferred:
Federal	(36,162		)	1,352			(4,720		)	(329,393		)
State	41			56			87			(43,990		)
Total deferred	(36,121		)	1,408			(4,633		)	(373,383		)
	$	(35,255	)	$	1,156		$	(4,626	)	$	(373,380	)

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



	Successor						Predecessor
	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016			Year Ended December 31, 2015
(In thousands)
Income tax provision (benefit) at statutory rate	$	71,118		$	12,112		$	433,109		$	(1,150,283	)
Percentage depletion allowance	(31,255		)	(4,292		)	(3,681		)	(19,035		)
State taxes, net of effect of federal taxes	7,002			633			(46,122		)	(76,445		)
Reversal of cancellation of indebtedness income	—			—			(1,493,162		)	—
Worthless stock deduction	—			—			(80,077		)	—
Change in valuation allowance	(410,983		)	(7,655		)	1,185,326			865,146
Impact of Tax Cuts and Jobs Act of 2017	332,345			—			—			—
Other, net	(3,482		)	358			(19		)	7,237
	$	(35,255	)	$	1,156		$	(4,626	)	$	(373,380	)

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



	December 31, 2017			December 31, 2016
(In thousands)
Deferred tax assets:
Tax loss carryforwards	$	271,405		$	376,293
Tax credit carryforwards	29,736			22,798
Investment in tax partnerships & corporations	308,653			604,914
Other	28,321			39,251
Gross deferred tax assets	638,115			1,043,256
Valuation allowance	(610,571		)	(1,021,553		)
Total deferred tax assets	27,544			21,703
Deferred tax liabilities:
Plant and equipment	3,674			7,332
Other	1,351			14,258
Total deferred tax liabilities	5,025			21,590
Net deferred tax asset	22,519			113

The Company has gross federal net operating loss carryforwards for regular income tax purposes of $980.2 million at December 31, 2017 that will expire between 2022 and 2037. The Company has an alternative minimum tax credit carryforward of $23.9 million at December 31, 2017, which has no expiration date and can be used to offset future regular tax in excess of the alternative minimum tax. The future annual usage of NOLs and AMT credit will be limited under IRC section 382.

As part of its efforts to create operational efficiency leading up to and through the bankruptcy process, the Company has consolidated its mining operations and land management into a partnership structure to match its legal form with the Company’s streamlined operations during 2016. As such, deferred taxes related to those operations are now reported based upon the book and tax outside basis difference in the partnership interests as provided in ASC 740-30-25-7, which results in a different basis of presentation than used in 2015 under the Company’s prior legal structure.

Valuation allowances were established in prior years for federal and state net operating losses and tax credits that were not offset by the reversal of other net taxable temporary differences before the expiration of the attribute.

At December 31, 2015, additional losses were realized relating primarily to financial conditions and asset impairment charges. As a result, the expected reversal of taxable temporary differences were not sufficient to support the future realization of the deferred tax assets and an additional $865.1 million valuation allowance was recorded. Net deferred tax assets of $1,135 million were completely offset by a valuation allowance.

At December 31, 2016, additional tax losses were realized primarily as a result of the non-recognition of CODI under section 108 of the IRC by the Predecessor entity. As a result, the expected reversal of taxable temporary differences were not sufficient to support the future realization of the deferred tax assets and an additional $1,185 million valuation allowance was recorded to the provision. Offsetting this increase was a net reduction in the valuation allowance of $1,289 million which did not impact the provision. This reduction was primarily the result of a decrease in NOLs and AMT credits due to the IRC section 108 offset rules. Net deferred tax assets of $1,022 million were completely offset by a valuation allowance.

On December 22, 2017 the Tax Cut and Jobs Act of 2017 (“the Act”) was signed into law making significant changes to the Internal Revenue Code. Changes include, but are not limited to, a corporate tax rate decrease from 35% to 21% effective for tax years beginning after December 31, 2017, the elimination of the corporate alternative minimum tax regime effective for tax years beginning after December 31, 2017, implementation of a process whereby corporations with unused alternative minimum tax credits will be refunded during 2018-2022, the transition of U.S. international taxation from a worldwide tax system to a territorial system, a one-time transition tax on the mandatory deemed repatriation of cumulative foreign earnings as of December 31, 2017, further limitation on the deductibility of certain executive compensation, allowance for immediate capital expensing of certain qualified property, and limitations on the amount of interest expense deductible beginning in 2018.

The Company has not completed its analysis for the income tax effects of the Act but has provided its best estimate of the impact of the Act in its year-end income tax provision in accordance with the guidance and interpretations available as of the date of this filing for the items noted below. The Company anticipates finalizing the analysis for the estimate by December 31, 2018, within the one year measurement period under SAB 118, for the following items:

•

Remeasurement of deferred taxes: deferred tax assets and liabilities attributable to the U.S. were remeasured from 35% to the reduced tax rate of 21%. The provisional amount related to the remeasurement of certain deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future was $330.9 million of income tax expense, with an offsetting valuation allowance adjustment. Finalization of the remeasurement of deferred taxes will occur upon finalization of 2017 taxable income and attribute carryback claims.

•

One-time transition tax on the mandatory deemed repatriation of cumulative foreign earnings: The provisional amount of income tax expense related to the mandatory deemed repatriation of foreign earnings was $1.5 million based on cumulative foreign earnings of $4.2 million. The deemed repatriation tax is completely offset with net operating loss carryforwards, with an offsetting valuation allowance adjustment and will not result in a cash tax liability. Finalization of 2017 earnings and profits calculations and receipt of further guidance in the form of Notices or Regulations may change the provisional calculation.

•

Elimination of the corporate AMT regime: Existing AMT credits as of December 31, 2017 will be refunded over the next four years. The refund may be subject to a sequestration reduction rate of approximately 6.6%. The Company has provisionally determined that it will receive a refund of existing AMT credits of approximately $22.4 million after an estimated sequestration reduction of $1.5 million. The valuation allowance previously recorded against these credits has been released and a tax benefit of $22.4 million was recorded. The Company’s accounting policy regarding the balance sheet presentation of the AMT credits is to record the balance as a deferred tax asset until a return is filed claiming a refund of a portion of the credit, at which time the amount will be presented as a tax receivable. Finalization of the AMT credit balance will occur upon finalization of 2017 taxable income and attribute carryback claims as well as the receipt of further guidance in the form of Notices or Regulations.

•

Elimination of executive compensation exemptions: The Act made changes to the $1 million limit on deductible compensation paid to certain “covered” employees. The Act eliminated exemptions for qualified performance based compensation and compensation paid after termination and expanded the number of employees to which the limit applies. The Company recorded a provisional amount of $0.2 million of tax expense, with an offsetting valuation allowance adjustment. The Act contains transitional rules, the implementation of which is uncertain at this time. The Company is still analyzing related aspects of the Act including the impact of the transitional rules. The provisional amount detailed above may change when further guidance is released that addresses these rules.

Other provisions in the Act that may impact the company in future years include limitations on interest expense deductions and the global intangible low-taxed income “GILTI” rules covering foreign income earned in low-tax countries. There was no impact recorded for these changes in the 2017 provision. Additional work is necessary to do a more detailed review of the Act, but is anticipated to be completed by December 31, 2018.

At December 31, 2017 additional tax losses were realized primarily as a result of the reversal of deductible temporary differences and percentage depletion. A $35.7 million benefit was recorded from the release of valuation allowance offsetting alternative minimum tax credits that have become refundable by the Act, as well as carryback claims filed in the fourth quarter related to specific liability losses that resulted in claims for refund of previously paid alternative minimum taxes. At December 31, 2017 a $610.5 million valuation allowance fully offsets all net deferred tax assets, other than alternative minimum tax credits.

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



		(In thousands)
Balance at	January 1, 2015	$	34,709
Additions based on tax positions related to the current year		4,168
Balance at	December 31, 2015	38,877
Additions based on tax positions related to the current year		2,979
Additions for tax positions of prior years		2,709
Reductions as a result of lapses in the statute of limitations		(37,110		)
Balance at	December 31, 2016	7,455
Additions for tax positions of prior years		—
Additions for tax positions related to the current year		3,928
Reductions as a result of bankruptcy		—
Balance at	December 31, 2017	$	11,383

If recognized, the entire amount of the gross unrecognized tax benefits at December 31, 2017 would affect the effective tax rate.

As a result of the bankruptcy, federal and state governments are precluded from assessing additional tax in audits of tax periods ending prior to bankruptcy. As a result, the Company has released $37.1 million of gross unrecognized tax benefits for years 2015 and prior. These gross unrecognized tax benefits are fully offset by a corresponding release in valuation allowance.

The Company recognizes interest and penalties related to unrecognized tax benefits in income tax expense. The Company had accrued interest and penalties of $0.6 million and $0.5 million at December 31, 2017 and 2016, respectively. In the next 12 months, $3.3 million gross unrecognized tax benefits are expected to be reduced due to the expiration of the statute of limitations.

Asset Retirement Obligations

12 Months Ended

Dec. 31, 2017

Asset Retirement Obligation [Abstract]

Asset Retirement Obligations

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

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



	Successor						Predecessor
	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016
(In thousands)
Balance at beginning of period (including current portion)	$	356,742		$	354,326		$	410,454
Accretion expense	30,209			7,634			24,321
Obligations of divested operations	(12,569		)	—			(14,702		)
Adjustments to the liability from changes in estimates	(23,215		)	—			3,003
Liabilities settled	(22,472		)	(5,218		)	(11,087		)
Fresh start accounting adjustment	—			—			(57,663		)
Balance at period end	$	328,695		$	356,742		$	354,326
Current portion included in accrued expenses	(19,840		)	(19,515		)	(17,290		)
Noncurrent liability	$	308,855		$	337,227		$	337,036

As of December 31, 2017, the Company had $531.7 million in surety bonds outstanding and $7.4 million in letters of credit to secure reclamation bonding obligations. Additionally, the Company has posted $2.6 million in cash as collateral related to reclamation surety bonds; this amount is recorded within “Noncurrent assets” on the Consolidated Balance Sheet.

Fair Value Measurements

12 Months Ended

Dec. 31, 2017

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 swaps and 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, coal commodity contracts and interest rate swaps 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 had a significant impact on the reported Level 3 fair values at December 31, 2017 and 2016.

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



	Fair Value at				December 31, 2017
	Total		Level 1			Level 2		Level 3
	(In thousands)
Assets:
Investments in marketable securities	$	155,846	$	64,100		$	91,746	$	—
Derivatives	7,339		—			1,985		5,354
Total assets	$	163,185	$	64,100		$	93,731	$	5,354
Liabilities:
Derivatives	$	7,217	$	7,263		$	26	$	(72	)



	Fair Value at					December 31, 2016
	Total		Level 1				Level 2		Level 3
	(In thousands)
Assets:
Investments in marketable securities	$	90,209	$	2,137			$	88,072	$	—
Derivatives	4,908		262				—		4,646
Total assets	$	95,117	$	2,399			$	88,072	$	4,646
Liabilities:
Derivatives	$	101	$	(8	)		$	—	$	109

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 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.



	Successor						Predecessor
	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016
(In thousands)
Balance, beginning of period	$	4,537		$	3,842		$	2,432
Realized and unrealized (gains) losses recognized in earnings, net	(2,305		)	926			(1,686		)
Included in other comprehensive income	—			—			—
Purchases	4,910			1,225			5,021
Issuances	(535		)	(34		)	(488		)
Settlements	(1,181		)	(1,422		)	(1,437		)
Ending balance	$	5,426		$	4,537		$	3,842

Net unrealized gains of $2.3 million were recognized during the year ended December 31, 2017 related to level 3 financial instruments held on December 31, 2017.

Cash and Cash Equivalents

At December 31, 2017 and 2016, the carrying amounts of cash and cash equivalents approximate their fair value.

Fair Value of Long-Term Debt

At December 31, 2017 and 2016, the fair value of the Company’s debt, including amounts classified as current, was $336.1 million and $362.9 million, 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

Capital Stock

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Capital Stock

Dividends

The Company declared and paid cash dividends per share during the periods presented below:



2017:	Dividends per share		Amount (in thousands)
1st quarter	$	—	$	—
2nd quarter	0.35		8,563
3rd quarter	0.35		8,200
4th quarter	0.35		7,606
Total cash dividends declared and paid	$	1.05	$	24,369

Future dividend declarations will be subject to ongoing Board review and authorization will be based on a number of factors, including business and market conditions, the Company’s future financial performance and other capital priorities.

Share Repurchase Program

During April 2017, the Board of Directors of Arch Coal, Inc. authorized a new share repurchase program for up to $300 million of its common stock. In October 2017, the Company’s Board of Directors approved an incremental $200 million increase to the share repurchase program bringing the total authorization to $500 million. Below is a table showing the share repurchase activity in 2017:



2017:	Number of Shares	Average Repurchase Price per Share		Amount (in thousands)
1st quarter	—	$	—	$	—
2nd quarter	710,701	$	71.82	51,043
3rd quarter	2,208,133	$	75.49	166,685
4th quarter	1,058,381	$	79.73	84,381
Total shares repurchased	3,977,215	$	75.96	$	302,109

The timing of any future share repurchases, and the ultimate number of shares purchased, will depend on a number of factors, including business and market conditions, the Company’s future financial performance and other capital priorities. The shares will be acquired in the open market or through private transactions in accordance with the Securities and Exchange Commission requirements. The share repurchase program has no termination date, but may be amended, suspended or discontinued at any time and does not commit the Company to repurchase shares of its common stock. The actual number and value of the shares to be purchased will depend on the performance of the Company’s stock price and other market conditions.

Outstanding Warrants

During 2017, holders of warrants had exercised 65,499 of the warrants, leaving 1,846,158 warrants outstanding at December 31, 2017.

As provided in ASC 825-20, “Financial Instruments,” the warrants are considered equity because they can only be physically settled in Company shares, can be settled in unregistered shares, the Company has adequate authorized shares to settle the outstanding warrants and each warrant is fixed in terms of settlement to one share of Company stock subject only to remote contingency adjustment factors designed to assure the relative value in terms of shares remains fixed.

Stock-Based Compensation and Other Incentive Plans

12 Months Ended

Dec. 31, 2017

Share-based Compensation [Abstract]

Stock-Based Compensation And Other Incentive Plans

Stock-Based Compensation and Other Incentive Plans

Under the Company’s 2016 Omnibus Incentive Plan (the “Incentive Plan”), 3.0 million shares of the Company’s common stock were reserved for awards to officers and other selected key management employees of the Company. The Incentive Plan provides the Board of Directors with the flexibility to grant stock options, stock appreciation rights, restricted stock awards, restricted stock units, performance stock or units, phantom stock awards and rights to acquire stock through purchase under a stock purchase program (“Awards”). Awards the Board of Directors elects to pay out in cash do not impact the shares authorized in the Incentive Plan. Shares available for award under the plan were 2.4 million at December 31, 2017.

Restricted Stock Unit Awards

The Company may issue restricted stock and restricted stock units, which require no payment from the employee. Restricted stock cliff-vests at various dates and restricted stock units either vest ratably over or vest at the end of the award’s stated vesting period. Compensation expense is based on the fair value on the grant date and is recorded ratably over the vesting period utilizing the straight-line recognition method. The employee receives cash compensation equal to the amount of dividends that would have been paid on the underlying shares.

During 2017, the Company granted both time based awards and performance based awards. The time based awards vest over either a one or three year period and the performance based awards vest over a three year period. The time based awards’ grant date fair value was determined based on the stock price at the date of grant. The performance awards grant date fair value was determined using a Black-Scholes Monte Carlo simulation. A volatility of 50% and 60% were selected for each of the performance-based awards based on comparator companies, and the three-year risk free rate was derived from yields on U.S. Government bonds. Information regarding the restricted stock units activity and weighted average grant-date fair value follows:



	Time Based Awards				Performance Based Awards
	Restricted Stock Units		Weighted Average Grant-Date Fair Value		Restricted Stock Units	Weighted Average Grant-Date Fair Value
(Shares in thousands)
Outstanding at January 1, 2017	159		$	78.60	225	$	67.34
Granted	92		81.91		86	101.38
Forfeited/Canceled	(2	)	78.60		—	—
Vested	(9	)	78.60		—	—
Unvested outstanding at December 31, 2017	240		$	79.87	311	$	76.75

The Company recognized expense related to restricted stock units of $10.4 million for the year ended December 31, 2017 and $1.0 million for the period October 2, 2016 through December 31, 2016. As of December 31, 2017, there was $32.4 million of unrecognized share-based compensation expense which is expected to be recognized over a weighted-average period of approximately three years.

Long-Term Incentive Compensation

The Company has a long-term incentive program that allows for the award of performance units. The total number of units earned by a participant is based on financial and operational performance measures, and may be paid out in cash or in shares of the Company’s common stock. The Company recognizes compensation expense over the three year term of the grant. The liabilities are remeasured quarterly. The Company recognized expense of $0.7 million for the year ended December 31, 2017, $1.6 million for the period October 2 through December 31, 2016, $7.2 million for the period January 1 through October 1, 2016 and $7.9 million for the year ended December 31, 2015, respectively. The expense is included primarily in “Selling, general and administrative expenses” in the accompanying consolidated statements of operations.

Amounts accrued and unpaid for all grants under the plan totaled $8.7 million and $13.9 million as of December 31, 2017 and 2016, respectively.

Workers' Compensation Expense

12 Months Ended

Dec. 31, 2017

Workers' Compensation Expense

Workers’ Compensation Expense

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

In addition, the Company is liable for workers’ compensation benefits for traumatic injuries which are calculated using actuarially-based loss rates, loss development factors and discounted based on a risk free rate of 2.43%. Traumatic workers’ compensation claims are insured with varying retentions/deductibles, or through state-sponsored workers’ compensation programs.

Workers’ compensation expense consists of the following components:



	Successor				Predecessor
	Year Ended December 31, 2017		October 2 through December 31, 2016		January 1 through October 1, 2016		Year Ended December 31, 2015
(In thousands)
Self-insured occupational disease benefits:
Service cost	$	6,320	$	1,583	$	3,465	$	4,282
Interest cost	4,651		1,126		3,184		3,944
Net amortization	—		—		4,325		6,973
Total occupational disease	$	10,971	$	2,709	$	10,974	$	15,199
Traumatic injury claims and assessments	3,208		3,162		6,628		16,781
Total workers’ compensation expense	$	14,179	$	5,871	$	17,602	$	31,980

The table below reconciles changes in the occupational disease liability for the respective period.



	Successor						Predecessor
(In thousands)	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016
Beginning of period	$	111,159		$	119,710		$	90,836
Service cost	6,320			1,583			3,465
Interest cost	4,651			1,126			3,184
Curtailments	(5,433		)	—			4,156
Actuarial (gain) loss	12,242			(9,675		)	—
Benefit and administrative payments	(6,513		)	(1,585		)	(3,728		)
Fresh start accounting adjustment	—			—			21,797
	$	122,426		$	111,159		$	119,710

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



	Successor		Predecessor
	Year Ended December 31, 2017	October 2 through December 31, 2016	January 1 through October 1, 2016
(Percentages)
Occupational Disease Benefit
Discount rate	3.66	4.31	3.80
Cost escalation rate	N/A	N/A	N/A

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



	Year Ended December 31, 2017		Year Ended December 31, 2016
(In thousands)
Occupational disease costs	$	122,426	$	111,159
Traumatic and other workers’ compensation claims	81,191		88,593
Total obligations	203,617		199,752
Less amount included in accrued expenses	18,782		15,184
Noncurrent obligations	$	184,835	$	184,568

As of December 31, 2017, the Company had $123.0 million in surety bonds and letters of credit outstanding to secure workers’ compensation obligations.

The Company’s recorded liabilities include $20.3 million of obligations that are reimbursable under various insurance policies purchased by the company. These insurance receivables are recorded in the balance sheet line items “Other receivables” and “Other noncurrent assets” for $3.3 million and $17.0 million, respectively.

Employee Benefit Plans

12 Months Ended

Dec. 31, 2017

Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]

Employee Benefit Plans

Defined Benefit Pension and Other Postretirement Benefit Plans

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

The Company also currently provides certain postretirement medical and life insurance coverage for eligible employees. Generally, covered employees who terminate employment after meeting eligibility requirements are eligible for postretirement coverage for themselves and their dependents. The Company offers a subsidy to eligible retirees based on age and years of service at retirement and contain other cost-sharing features such as deductibles and coinsurance. The Company’s current funding policy is to fund the cost of all postretirement benefits as they are paid.

On January 1, 2015, the Company’s cash balance and excess plans were amended to freeze new service credits for any new or active employee.

Obligations and Funded Status.

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



	Pension Benefits									Other Postretirement Benefits
	Successor						Predecessor			Successor						Predecessor
	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016			Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016
(In thousands)
CHANGE IN BENEFIT OBLIGATIONS
Benefit obligations at beginning of period	$	313,629		$	341,427		$	301,292		$	111,867		$	120,311		$	103,460
Service cost	—			—			—			671			180			393
Interest cost	11,169			2,768			9,338			4,150			978			3,223
Divestitures (see Note 5 to the Consolidated Financial Statements)	(29,097		)	—			—			—			—			—
Settlements	(1,532		)	(135		)	—			—			—			—
Curtailments	—			—			454			(520		)	—			714
Benefits paid	(38,197		)	(11,009		)	(8,699		)	(8,152		)	(1,962		)	(8,273		)
Other-primarily actuarial (gain) loss	14,126			(19,422		)	—			2,503			(7,640		)	—
Fresh start accounting adjustments	—			—			39,042			—			—			$	20,794
Benefit obligations at end of period	$	270,098		$	313,629		$	341,427		$	110,519		$	111,867		$	120,311
CHANGE IN PLAN ASSETS
Value of plan assets at beginning of period	$	274,225		$	292,726		$	273,499		$	—		$	—		$	—
Actual return on plan assets	39,689			(7,899		)	27,811						—			—
Employer contributions	429			407			115			8,152			1,962			8,273
Benefits paid	(38,197		)	(11,009		)	(8,699		)	(8,152		)	(1,962		)	(8,273		)
Divestitures	$	(20,504	)	$	—		$	—		$	—		$	—		$	—
Value of plan assets at end of period	$	255,642		$	274,225		$	292,726		$	—		$	—		$	—
Accrued benefit cost	$	(14,456	)	$	(39,404	)	$	(48,701	)	$	(110,519	)	$	(111,867	)	$	(120,311	)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit (cost)	$	—		$	—		$	—		$	—		$	—		$	—
Accumulated gain	16,178			6,751			—			5,137			7,640			—
	$	16,178		$	6,751		$	—		$	5,137		$	7,640		$	—
BALANCE SHEET AMOUNTS
Current liability	$	(420	)	$	(520	)	$	(420	)	$	(8,150	)	$	(10,422	)	$	(8,352	)
Noncurrent liability	(14,036		)	(38,884		)	(48,281		)	(102,369		)	(101,445		)	(111,959		)
	$	(14,456	)	$	(39,404	)	$	(48,701	)	$	(110,519	)	$	(111,867	)	$	(120,311	)

Pension Benefits

The accumulated benefit obligation for all pension plans was $270.1 million and $313.6 million at December 31, 2017 and 2016, respectively.

Due to the Company adopting the corridor method of amortizing actuarial gains (losses) during fresh start accounting, it is anticipated there will be no amortization recorded into net periodic benefit cost during 2018.

Other Postretirement Benefits

Components of Net Periodic Benefit Cost. The following table details the components of pension and postretirement benefit costs (credits):



	Pension Benefits												Other Postretirement Benefits
	Successor						Predecessor						Successor					Predecessor
	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016			Year Ended December 31, 2015			Year Ended December 31, 2017			October 2 through December 31, 2016		January 1 through October 1, 2016			Year Ended December 31, 2015
(In thousands)
Service cost	$	—		$	—		$	—		$	9		$	671		$	180	$	393		$	866
Interest cost	11,169			2,768			9,338			14,604			4,150			978		3,223			1,904
Curtailments	—			—			454			—			(520		)	—		(970		)	—
Settlements	(1,532		)	(135		)	—			2,656			—			—		—			—
Expected return on plan assets	(16,498		)	(4,770		)	(13,623		)	(20,367		)	—			—		—			—
Amortization of prior service credits	—			—			—			—			—			—		(7,854		)	(8,335		)
Amortization of other actuarial losses (gains)	—			—			3,973			8,850			—			—		(849		)	(2,109		)
Net benefit cost (credit)	$	(6,861	)	$	(2,137	)	$	142		$	5,752		$	4,301		$	1,158	$	(6,057	)	$	(7,674	)

The differences generated from changes in assumed discount rates and returns on plan assets are amortized into earnings over the remaining service attribution periods of the employees using the corridor method.

Assumptions. The following table provides the weighted average assumptions used to determine the actuarial present value of projected benefit obligations for the respective periods.



	Successor		Predecessor
	Year Ended December 31, 2017	October 2 through December 31, 2016	January 1 through October 1, 2016
(Percentages)
Pension Benefits
Discount rate	3.49/3.27	3.95	3.39
Rate of compensation increase	N/A	N/A	N/A

Other Postretirement Benefits
Discount rate	3.49	3.93	3.37
Rate of compensation increase	N/A	N/A	N/A

The following table provides the weighted average assumptions used to determine net periodic benefit cost for the respective periods.



	Successor		Predecessor
	Year Ended December 31, 2017	October 2 through December 31, 2016	January 1 through October 1, 2016	Year Ended December 31, 2015
(Percentages)
Pension Benefits
Discount rate	3.77	3.39/3.95	4.59/3.80	4.15/4.61/4.41/4.60
Rate of compensation increase	N/A	N/A	N/A	N/A
Expected return on plan assets	6.20	6.85	6.85	7.00

Other Postretirement Benefits
Discount rate	3.85	3.37	4.57/3.80	3.91
Rate of compensation increase	N/A	N/A	N/A	N/A
Expected return on plan assets	N/A	N/A	N/A	N/A

The discount rates used in 2017, 2016 and 2015 were reevaluated during the year for settlements and curtailments. The obligations are remeasured at an updated discount rate that impacts the benefit cost recognized subsequent to the remeasurement.

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

The health care cost trend rate assumed for 2018 is 6.2% and is expected to reach an ultimate trend rate of 4.5% by 2038. A one-percentage-point increase in the health care cost trend rate would increase the postretirement benefit obligation at December 31, 2017 by $11.6 million and the net periodic postretirement benefit cost for the year ended December 31, 2017 by $0.4 million.

Plan Assets

The Pension Committee is responsible for overseeing the investment of pension plan assets. The Pension Committee is responsible for determining and monitoring appropriate asset allocations and for selecting or replacing investment managers, trustees and custodians. The pension plan’s current investment targets are 39% equity and 61% fixed income securities. The Pension Committee reviews the actual asset allocation in light of these targets on a periodic basis and rebalances among investments as necessary. The Pension Committee evaluates the performance of investment managers as compared to the performance of specified benchmarks and peers and monitors the investment managers to ensure adherence to their stated investment style and to the plan’s investment guidelines.

The Company’s pension plan assets at December 31, 2017 and 2016, respectively, are categorized below according to the fair value hierarchy as defined in Note 17, “Fair Value Measurements”:



	Total						Level 1				Level 2				Level 3
	2017			2016			2017		2016		2017		2016		2017		2016
	(In thousands)
Equity Securities:^(A)
U.S. small-cap	$	5,064		$	13,520		$	5,064	$	13,520	$	—	$	—	$	—	$	—
U.S. mid-cap	22,640			29,687			6,017		9,422		16,623		20,265		—		—
U.S. large-cap	43,232			70,226			21,416		34,107		21,816		36,119		—		—
Non-U.S.	10,115			18,937			—		—		10,115		18,937		—		—
Fixed income securities:																	—
U.S. government securities^(B)	66,922			26,519			60,286		19,973		6,636		6,546		—		—
Non-U.S. government securities^(C)	4,050			1,567			—		—		4,050		1,567		—		—
U.S. government asset and mortgage backed securities^(D)	2,440			1,074			—		—		2,440		1,074		—		—
Corporate fixed income^(E)	54,679			58,191			—		—		54,679		58,191		—		—
State and local government securities^(F)	3,829			6,406			—		—		3,829		6,406		—		—
Other investments^(I)	27,057			26,151			—		—		8,457		6,910		18,600		19,241
Total	$	240,028		$	252,278		$	92,783	$	77,022	$	128,645	$	156,015	$	18,600	$	19,241
Other fixed income^(G)	16,646			35,519
Short-term investments^(H)	8,573			8,598
Other liabilities^(J)	(9,605		)	(22,170		)
	$	255,642		$	274,225

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

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

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

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

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

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

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

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

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

^(J)Net payable amount due for pending securities purchased and sold due to broker/dealer.

Cash Flows. The Company expects to make contributions of $0.4 million to the pension plans in 2018, which is impacted by the Moving Ahead for Progress in the 21st Century Act (MAP-21). MAP-21 does not reduce the Company’s obligations under the plan, but redistributes the timing of required payments by providing near term funding relief for sponsors under the Pension Protection Act.

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



			Other
	Pension		Postretirement
	Benefits		Benefits
	(In thousands)
2018	$	17,614	$	12,381
2019	17,834		12,549
2020	18,174		12,990
2021	18,635		13,239
2022	19,235		13,423
Next 5 years	83,071		62,854
	$	174,563	$	127,436

Other Plans

The Company sponsors savings plans which were established to assist eligible employees in providing for their future retirement needs. The Company’s expense, representing its contributions to the plans, was $18.0 million for the year ended December 31, 2017; $3.5 million for the period October 2 through December 31, 2016; $13.8 million for the period January 1 through October 1, 2016; and $20.5 million for the year ended December 31, 2015, respectively.

Earnings (Loss) Per Common Share

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Earnings (Loss) Per Common Share

The Company computes basic net income per share using the weighted average number of common shares outstanding during the period. Diluted net income per share is computed using the weighted average number of common shares and the effect of potentially dilutive securities outstanding during the period. Potentially dilutive securities may consist of warrants, restricted stock units or other contingently issuable shares. The dilutive effect of outstanding warrants, restricted stock units and other contingently issuable shares is reflected in diluted earnings per share by application of the treasury stock method.

The following table provides the basis for basic and diluted EPS by reconciling the numerators and denominators of the computations:



	Successor		Predecessor
	Year Ended December 31, 2017	October 2 through December 31, 2016	January 1 through October 1, 2016	Year Ended December 31, 2015
(In Thousands)
Weighted average shares outstanding:
Basic weighted average shares outstanding	23,725	25,002	21,293	21,285
Effect of dilutive securities	515	467	20	—

Diluted weighted average shares outstanding	24,240	25,469	21,313	21,285

Leases

12 Months Ended

Dec. 31, 2017

Leases [Abstract]

Leases

The Company leases equipment, land and various other properties under non-cancelable long-term leases, expiring at various dates. Certain leases contain options that would allow the Company to extend the lease or purchase the leased asset at the end of the base lease term.

In addition, the Company enters into various non-cancelable royalty lease agreements under which future minimum payments are due.

Minimum payments due in future years under these agreements in effect at December 31, 2017 are as follows:



	Operating
	Leases		Royalties
	(In thousands)
2018	$	5,936	$	3,582
2019	4,655		5,926
2020	2,260		6,953
2021	1,985		7,216
2022	2,024		7,003
Thereafter	8,292		34,371
	$	25,152	$	65,051

The Company has no obligations for future minimum payments under capital leases for equipment at December 31, 2017 and 2016.

Rental expense, including amounts related to these operating leases and other shorter-term arrangements, amounted to $19.2 million in 2017, $5.0 million for the period October 2 through December 31, 2016, $19.4 million for the period January 1 through October 1, 2016 and $28.4 million in 2015.

Royalties are paid to lessors either as a fixed price per ton or as a percentage of the gross selling price of the mined coal. Royalties under the majority of the Company’s significant leases are paid on the percentage of gross selling price basis. Royalty expense, including production royalties, was $167.4 million in 2017, $45.3 million for the period October 2 through December 31, 2016, $116.4 million for the period January 1 through October 1, 2016 and $227.7 million in 2015.

As of December 31, 2017, certain of the Company’s lease obligations were secured by outstanding surety bonds totaling $31.2 million.

Risk Concentrations

12 Months Ended

Dec. 31, 2017

Risks Concentrations [Abstract]

Risk Concentrations

Credit Risk and Major Customers

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

The Company markets its steam coal principally to domestic and foreign electric utilities and its metallurgical coal to domestic and foreign steel producers. As of December 31, 2017 and 2016, accounts receivable from electric utilities of $72.9 million and $96.0 million, respectively, represented 42% and 52% of total trade receivables at each date. As of December 31, 2017 and 2016, accounts receivable from sales of metallurgical-quality coal of $99.4 million and $88.0 million, respectively, represented 58% and 48% of total trade receivables at each date.

The Company uses shipping destination as the basis for attributing revenue to individual countries. Because title may transfer on brokered transactions at a point that does not reflect the end usage point, they are reflected as exports, and attributed to an end delivery point if that knowledge is known to the Company. The Company’s foreign revenues by geographical location are as follows:



	Successor				Predecessor
	Year Ended December 31, 2017		October 2 through December 31, 2016		January 1 through October 1, 2016		Year Ended December 31, 2015
(In thousands)
Europe	$	388,926	$	61,408	$	113,888	$	170,314
Asia	264,503		55,634		68,536		96,523
North America	88,145		43,831		56,594		40,315
Central and South America	30,982		13,224		41,861		55,323
Africa	14,901		—		—		—
Brokered Sales	6,137		—		—		32,848
Total	$	793,594	$	174,097	$	280,879	$	395,323

The Company is committed under long-term contracts to supply steam coal that meets certain quality requirements at specified prices. These prices are generally adjusted based on market indices. Quantities sold under some of these contracts may vary from year to year within certain limits at the option of the customer based on their requirements. The Company sold approximately 98.2 million tons of coal in 2017. Approximately 66% of this tonnage (representing approximately 55% of the Company’s revenues) was sold under long-term contracts (contracts having a term of greater than one year). Long-term contracts range in remaining life from one to four years.

Third-party sources of coal

The Company purchases coal from third parties that it sells to customers. Factors beyond the Company’s control could affect the availability of coal purchased by the Company. Disruptions in the quantities of coal purchased by the Company could impair its ability to fill customer orders or require it to purchase coal from other sources at prevailing market prices in order to satisfy those orders.

Transportation

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

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and 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. The Company is a party to numerous claims and lawsuits with respect to various matters. As of December 31, 2017 and 2016, the Company had accrued $0.2 million and $2.2 million, respectively, for all legal matters, including $0.2 million and $2.2 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. The Company has unconditional purchase obligations relating to purchases of coal, materials and supplies and capital commitments, other than reserve acquisitions, and is also a party to transportation capacity commitments. The future commitments under these agreements total $97.2 million in 2018, and is immaterial thereafter. The Company recognized expense relating to transportation capacity agreements of $1.6 million during the period January 1 through October 1, 2016; and $52.9 million during the year ended December 31, 2015, respectively.

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On February 13, 2018, the Company’s board of directors announced an increase in the Company’s quarterly dividend to $0.40 per common share from $0.35 per common share. The next quarterly cash dividend payment of $0.40 per common share is scheduled to be paid on March 15, 2018 to stockholders of record at the close of business on March 5, 2018.

Segment Information

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Segment Information

The Company’s reportable business segments are based on two distinct lines of business, metallurgical coal and thermal coal, and may include a number of mine complexes. The Company manages its coal sales by market, not by individual mining complex. Geology, coal transportation routes to customers, and regulatory environments also have a significant impact on the Company’s marketing and operations management. Mining operations are evaluated based on Adjusted EBITDAR, per-ton cash operating costs (defined as including all mining costs except depreciation, depletion, amortization, accretion on asset retirement obligations, and pass-through transportation expenses), and on other non-financial measures, such as safety and environmental performance. Adjusted EBITDAR is not a measure of financial performance in accordance with generally accepted accounting principles, and items excluded from Adjusted EBITDAR are significant in understanding and assessing our financial condition. Therefore, Adjusted EBITDAR should not be considered in isolation, nor as an alternative to net income, income from operations, cash flows from operations or as a measure of our profitability, liquidity or performance under generally accepted accounting principles. The Company uses Adjusted EBITDAR to measure the operating performance of its segments and allocate resources to the segments. Furthermore, analogous measures are used by industry analysts and investors to evaluate the Company’s operating performance. Investors should be aware that the Company’s presentation of Adjusted EBITDAR may not be comparable to similarly titled measures used by other companies. The Company reports its results of operations primarily through the following reportable segments: Powder River Basin (PRB) segment containing the Company’s primary thermal operations in Wyoming; the Metallurgical (MET) segment, containing the Company’s metallurgical operations in West Virginia, Kentucky, and Virginia, and the Other Thermal segment containing the Company’s supplementary thermal operations in Colorado, Illinois, and West Virginia. Periods presented in this note have been recast for comparability.

On September 14, 2017, the Company closed on its’ definitive agreement to sell Lone Mountain Processing LLC, an operating mine complex within the Company’s metallurgical coal segment. Through this transaction the Company divested all active operations in the states of Kentucky and Virginia. For further information on the divestiture, please see Note 5 to the Consolidated Financial Statements, “Divestitures.”

Operating segment results for the year ended December 31, 2017, the Successor period October 2 through December 31, 2016 and the Predecessor periods January 1 through October 1, 2016 and the year ended December 31, 2015 are presented below. The Company measures its segments based on “adjusted earnings before interest, taxes, depreciation, depletion, amortization, accretion on asset retirements obligations, and reorganization items, net (Adjusted EBITDAR).” Adjusted EBITDAR does not reflect mine closure or impairment costs, since those are not reflected in the operating income reviewed by management. See Note 6, “Impairment Charges and Mine Closure Costs” for discussion of these costs. The Corporate, Other and Eliminations grouping includes these charges, as well as the change in fair value of coal derivatives and coal trading activities, net; corporate overhead; land management activities; other support functions; and the elimination of intercompany transactions.



(In thousands)		PRB		MET		Other Thermal		Corporate, Other and Eliminations			Consolidated
Successor Year Ended	December 31, 2017
Revenues		$	1,024,197	$	887,839	$	396,504	$	16,083		$2,324,623
Adjusted EBITDAR		158,882		243,616		102,006		(86,747		)	417,757
Depreciation, depletion and amortization		36,349		70,896		13,588		1,631			122,464
Accretion on asset retirement obligation		20,160		2,000		2,161		5,888			30,209
Total Assets		390,665		548,476		134,397		906,094			1,979,632
Capital expenditures		6,212		32,678		11,901		8,414			59,205
Successor Period	October 2 through December 31, 2016
Revenues		$	275,703	$	200,377	$	97,382	$	2,226		$575,688
Adjusted EBITDAR		55,765		30,819		31,159		(23,246		)	94,497
Depreciation, depletion and amortization		9,949		18,287		3,911		457			32,604
Accretion on asset retirement obligation		5,049		528		540		1,517			7,634
Total assets		446,775		576,793		129,602		983,427			2,136,597
Capital expenditures		934		13,329		684		267			15,214
Predecessor Period	January 1 through October 1, 2016
Revenues		$	726,747	$	437,069	$	213,052	$	21,841		$1,398,709
Adjusted EBITDAR		113,185		11,851		31,448		(69,181		)	87,303
Depreciation, depletion and amortization		100,151		55,311		32,310		3,809			191,581
Accretion on asset retirement obligation		16,940		1,765		1,988		3,628			24,321
Total assets		456,711		619,154		131,173		916,791			2,123,829
Capital expenditures		612		17,296		3,895		60,631			82,434
Predecessor Year Ended	December 31, 2015
Revenues		$	1,448,440	$	637,941	$	428,809	$	58,070		$	2,573,260
Adjusted EBITDAR		281,039		70,450		42,734		(110,426		)	283,797
Depreciation, depletion and amortization		176,257		133,463		47,786		21,839			379,345
Accretion on asset retirement obligation		22,156		2,267		2,658		6,599			33,680
Total assets		1,648,916		772,439		366,610		2,253,916			5,041,881
Capital expenditures		21,228		24,787		11,277		61,732			119,024

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



	Successor					Predecessor
(In thousands)	Year Ended December 31, 2017			October 2 through December 31, 2016		January 1 through October 1, 2016			Year Ended December 31, 2015

Income (loss) before income taxes	$	203,195		$	34,605	$	1,237,455		$	(3,286,522	)
Interest expense, net	24,256			10,754		133,235			393,549
Depreciation, depletion and amortization	122,464			32,604		191,581			379,345
Accretion on asset retirement obligations	30,209			7,634		24,321			33,680
Amortization of sales contracts, net	53,985			796		(728		)	(8,811		)
Asset impairment and mine closure costs	—			—		129,267			2,628,303
Losses from disposed operations resulting from Patriot Coal bankruptcy	—			—		—			116,343
Gain on sale of Lone Mountain Processing, Inc.	(21,297		)	—		—			—
Net loss resulting from early retirement of debt and debt restructuring	2,547			—		2,213			27,910
Reorganization items, net	2,398			759		(1,630,041		)	—
Fresh start coal inventory fair value adjustment	—			7,345		—			—
Adjusted EBITDAR	$	417,757		$	94,497	$	87,303		$	283,797

Quarterly Selected Financial Data (unaudited)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Quarterly Selected Financial Data (unaudited)



Year Ended December 31, 2017	March 31			June 30			September 30			December 31

(In thousands, except per share data)

Revenues	$	600,975		$	549,866		$	613,538		560,244
Gross profit	$	85,747		$	62,577		$	65,100		62,937
Income from operations	$	66,264		$	42,692		$	72,489		$	50,951
Reorganization items, net	$	(2,828	)	$	(21	)	$	(43	)	$	494
Net income	$	51,668		$	37,160		$	68,351		$	81,271
Diluted income per common share	$	2.03		$	1.48		$	2.83		$	3.64



	Predecessor											Successor
Year Ended December 31, 2016	March 31			June 30			September 30			October 1		October 2 through December 31, 2016
	(a) (b)			(a) (b)			(b)			(b)
(In thousands, except per share data)

Revenues	$	428,106		$	420,298		$	550,305		$	—	$	575,688
Gross profit (loss)	$	(53,325	)	$	(56,469	)	$	31,042		$	—	$	64,458
Asset impairment and mine closure costs	$	85,520		$	43,701		$	46		$	—	$	—
Income (loss) from operations	$	(158,412	)	$	(110,521	)	$	11,795		$	—	$	46,118
Reorganization items, net	$	(3,875	)	$	(21,271	)	$	(20,904	)	$	1,676,091	$	(759	)
Net income (loss)	$	(206,702	)	$	(175,887	)	$	(51,421	)	$	1,676,091	$	33,449
Diluted income (loss) per common share	$	(9.71	)	$	(8.26	)	$	(2.41	)	$	78.66	$	1.31

(a) Challenging coal markets resulted in impairment charges relating to leased mineral reserves, prepaid mining royalties, investments in equity method subsidiaries and severance expense in 2016. See further discussion in Note 6, “Impairment Charges and Mine Closure Costs “ and Note 10, “Equity Method Investments and Membership Interests in Joint Ventures.”

(b) The Company filed for bankruptcy on January 11, 2016 and subsequently emerged on October 5, 2016. See further discussion in Note 3, “Emergence from Bankruptcy and Fresh Start Accounting.”

Valuation and Qualifying Accounts

12 Months Ended

Dec. 31, 2017

Valuation and Qualifying Accounts [Abstract]

Valuation and Qualifying Accounts



			Additions
			(Reductions)
	Balance at		Charged to			Charged to						Balance at
	Beginning of		Costs and			Other						End of
	Year		Expenses			Accounts				Deductions ^(a)		Year
	(In thousands)

Year Ended December 31, 2017
Reserves deducted from asset accounts:
Accounts receivable and other receivables	$	—										$	—
Current assets — supplies and inventory	—		365			(17		)	^(b)	87		261
Deferred income taxes	1,021,553		(410,982		)							610,571
Successor
October 2 through December 31, 2016
Reserves deducted from asset accounts:
Accounts receivable and other receivables	$	—	$	—		$	—			$	—	$	—
Current assets — supplies and inventory	—		—			—				—		—
Deferred income taxes	1,033,982		(12,429		)	—				—		1,021,553
Predecessor
January 1 through October 1, 2016
Reserves deducted from asset accounts:
Accounts receivable and other receivables	$	7,842	$	—		$	—			$	7,842	$	—
Current assets — supplies and inventory	5,991		844			(5,060		)	^(c)	1,775		—
Deferred income taxes	1,135,399		(101,417		)					—		1,033,982
Year ended December 31, 2015
Reserves deducted from asset accounts:
Accounts receivable and other receivables	$	159	$	7,683		$	—			$	—	$	7,842
Current assets — supplies and inventory	6,625		431			—				1,065		5,991
Deferred income taxes	270,251		865,148			—				—		1,135,399

(a) Reserves utilized, unless otherwise indicated.

(b) Disposition of subsidiaries

Accounting Policies (Policies)	12 Months Ended
Accounting Policies (Policies)	Dec. 31, 2017
Accounting Policies [Abstract]
Consolidation Policy	The accompanying consolidated financial statements include the accounts of Arch Coal, Inc. and its subsidiaries and controlled entities (the “Company”). Unless the context indicates otherwise, the terms “Arch” and the “Company” are used interchangeably in this Annual Report on Form 10-K refer to both the Predecessor and Successor 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, Illinois, Wyoming and Colorado. All subsidiaries are wholly-owned. Intercompany transactions and accounts have been eliminated in consolidation.
Accounting Estimates	Accounting Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and revenues and expenses in the accompanying consolidated financial statements and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents are stated at cost. Cash equivalents consist of highly-liquid investments with an original maturity of three months or less when purchased.
Restricted cash	Restricted cash Restricted cash represents cash collateral supporting letters of credit issued under the Company’s accounts receivable securitization program.
Accounts Receivable	Accounts Receivable Accounts receivable are recorded at amounts that are expected to be collected, based on past collection history, the economic environment and specified risks identified in the receivables portfolio.
Inventories	Inventories Coal and supplies inventories are valued at the lower of average cost or market. Coal inventory costs include labor, supplies, equipment costs, transportation costs incurred prior to the transfer of title to customers and operating overhead. The costs of removing overburden, called stripping costs, incurred during the production phase of the mine are considered variable production costs and are included in the cost of the coal extracted during the period the stripping costs are incurred.
Investments and Membership Interests in Joint Ventures	Investments and Membership Interests in Joint Ventures Investments and membership interests in joint ventures are accounted for under the equity method of accounting if the Company has the ability to exercise significant influence, but not control, over the entity. The Company’s share of the entity’s income or loss is reflected in “Other operating expense (income), net” in the consolidated statements of operations. Information about investment activity is provided in Note 10 to the Consolidated Financial Statements, “Equity Method Investments and Membership Interests in Joint Ventures.” Investments in debt securities and marketable equity securities that do not qualify for equity method accounting are classified as available-for-sale and are recorded at their fair values. Unrealized gains and losses on these investments are recorded in other comprehensive income or loss. A decline in the value of an investment that is considered other-than-temporary would be recognized in operating expenses.
Sales Contracts	Sales Contracts Coal supply agreements (sales contracts) valued during fresh start accounting or acquired in a business combination are capitalized at their fair value and amortized over the tons of coal shipped during the term of the contract. The fair value of a sales contract is determined by discounting the cash flows attributable to the difference between the contract price and the prevailing forward prices for the tons under contract at the date of acquisition. See Note 11 to the Consolidated Financial Statements, “Sales Contracts” for further information related to the Company’s sales contracts.
Exploration Costs	Exploration Costs Costs to acquire permits for exploration activities are capitalized. Drilling and other costs related to locating coal deposits and evaluating the economic viability of such deposits are expensed as incurred.
Prepaid Royalties	Prepaid Royalties Leased mineral rights are often acquired through royalty payments. When royalty payments represent prepayments recoupable against royalties owed on future revenues from the underlying coal, they are recorded as a prepaid asset, with amounts expected to be recouped within one year classified as current. When coal from these leases is sold, the royalties owed are recouped against the prepayment and charged to cost of sales. An impairment charge is recognized for prepaid royalties that are not expected to be recouped.
Property, Plant and Equipment	Property, Plant and Equipment Plant and Equipment Plant and equipment were recorded at fair value at emergence during fresh start accounting; subsequent purchases of property, plant and equipment have been recorded at cost. Interest costs incurred during the construction period for major asset additions are capitalized. The Company did not capitalize any interest costs during years ended December 31, 2017 and 2016, respectively. Expenditures that extend the useful lives of existing plant and equipment or increase the productivity of the asset are capitalized. The cost of maintenance and repairs that do not extend the useful life or increase the productivity of the asset is expensed as incurred. Preparation plants and loadouts are depreciated using the units-of-production method over the estimated recoverable reserves, subject to a minimum level of depreciation. Other plant and equipment are depreciated principally using the straight-line method over the estimated useful lives of the assets, limited by the remaining life of the mine. The useful lives of mining equipment, including longwalls, draglines and shovels, range from 7 to 18 years. The useful lives of buildings and leasehold improvements generally range from 1 to 21 years. Deferred Mine Development Costs of developing new mines or significantly expanding the capacity of existing mines are capitalized and amortized using the units-of-production method over the estimated recoverable reserves that are associated with the property being benefited. Costs may include construction permits and licenses; mine design; construction of access roads, shafts, slopes and main entries; and removing overburden to access reserves in a new pit. Additionally, deferred mine development includes the asset cost associated with asset retirement obligations. Coal sales revenue related to incidental production during the development phase will be recorded as coal sales revenue with an offset to cost of coal sales based on the estimated cost per ton sold for the mine when the asset is in place for its intended use. Coal Lands and Mineral Rights Rights to coal reserves may be acquired directly through governmental or private entities. A significant portion of the Company’s coal reserves are controlled through leasing arrangements. Lease agreements are generally long-term in nature (original terms range from 10 to 50 years), and substantially all of the leases contain provisions that allow for automatic extension of the lease term providing certain requirements are met. The net book value of the Company’s coal interests was $361.2 million and $381.0 million at December 31, 2017 and 2016, respectively. Payments to acquire royalty lease agreements and lease bonus payments are capitalized as a cost of the underlying mineral reserves and depleted over the life of proven and probable reserves. Coal lease rights are depleted using the units-of-production method, and the rights are assumed to have no residual value. The Company currently does not have any future lease bonus payments. Depreciation, depletion and amortization The depreciation, depletion and amortization related to long-lived assets is reflected in the statement of operations as a separate line item. No depreciation, depletion or amortization is included in any other operating cost categories. Impairment If facts and circumstances suggest that the carrying value of a long-lived asset or asset group may not be recoverable, the asset or asset group is reviewed for potential impairment. If this review indicates that the carrying amount of the asset will not be recoverable through projected undiscounted cash flows generated by the asset and its related asset group over its remaining life, then an impairment loss is recognized by reducing the carrying value of the asset to its fair value. The Company may, under certain circumstances, idle mining operations in response to market conditions or other factors. Because an idling is not a permanent closure, it is not considered an automatic indicator of impairment. See additional discussion in Note 6 to the Consolidated Financial Statements, “Impairment Charges and Mine Closure Costs.”
Deferred Financing Costs	Deferred Financing Costs The Company capitalizes costs incurred in connection with new borrowings, the establishment or enhancement of credit facilities and the issuance of debt securities. These costs are amortized as an adjustment to interest expense over the life of the borrowing or term of the credit facility using the interest method. Debt issuance costs related to a recognized liability are presented in the balance sheet as a direct reduction from the carrying amount of that liability whereas debt issuance costs related to a credit facility with no balance outstanding are shown as an asset.
Revenue Recognition	Revenue Recognition Revenues include sales to customers of coal produced at Company operations and coal purchased from third parties. The Company recognizes revenue at the time risk of loss passes to the customer at contracted amounts. Transportation costs are included in cost of sales and amounts billed by the Company to its customers for transportation are included in revenues.
Other Operating Expense (Income), net	Other Operating Expense (Income), net Other operating expense (income), net in the accompanying consolidated statements of operations reflects income and expense from sources other than physical coal sales, including: bookouts, or the practice of offsetting purchase and sale contracts for shipping convenience purposes; contract settlements; liquidated damage charges related to unused terminal and port capacity; royalties earned from properties leased to third parties; income from equity investments (Note 10, “Equity Method Investments and Membership Interests in Joint Ventures”); non-material gains and losses from divestitures and dispositions of assets; and realized gains and losses on derivatives that do not qualify for hedge accounting and are not held for trading purposes (Note 12, “Derivatives”).
Asset Retirement Obligations	Asset Retirement Obligations The Company’s legal obligations associated with the retirement of long-lived assets are recognized at fair value at the time the obligations are incurred. Accretion expense is recognized through the expected settlement date of the obligation. Obligations are incurred at the time development of a mine commences for underground and surface mines or construction begins for support facilities, refuse areas and slurry ponds. The obligation’s fair value is determined using a discounted cash flow technique and is based upon permit requirements and various estimates and assumptions that would be used by market participants, including estimates of disturbed acreage, reclamation costs and assumptions regarding equipment productivity. Upon initial recognition of a liability, a corresponding amount is capitalized as part of the carrying value of the related long-lived asset. The Company reviews its asset retirement obligation at least annually and makes necessary adjustments for permit changes as granted by state authorities and for revisions of estimates of the amount and timing of costs. For ongoing operations, adjustments to the liability result in an adjustment to the corresponding asset. For idle operations, adjustments to the liability are recognized as income or expense in the period the adjustment is recorded. Any difference between the recorded obligation and the actual cost of reclamation is recorded in profit or loss in the period the obligation is settled.
Loss Contingencies	Loss 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. The amount accrued represents the Company’s best estimate of the loss, or, if no best estimate within a range of outcomes exists, the minimum amount in the range.
Derivative Instruments	Derivative Instruments The Company generally utilizes derivative instruments to manage exposures to commodity prices and interest rate risk on long-term debt. Additionally, the Company may hold certain coal derivative instruments for trading purposes. Derivative financial instruments are recognized in the balance sheet at fair value. Certain coal contracts may meet the definition of a derivative instrument, but because they provide for the physical purchase or sale of coal in quantities expected to be used or sold by the Company over a reasonable period in the normal course of business, they are not recognized on the balance sheet. Certain derivative instruments are designated as the hedge instrument in a hedging relationship. In a fair value hedge, the Company hedges the risk of changes in the fair value of a firm commitment, typically a fixed-price coal sales contract. Changes in both the hedged firm commitment and the fair value of a derivative used as a hedge instrument in a fair value hedge are recorded in earnings. In a cash flow hedge, the Company hedges the risk of changes in future cash flows related to the underlying item being hedged. Changes in the fair value of the derivative instrument used as a hedge instrument in a cash flow hedge are recorded in other comprehensive income or loss. Amounts in other comprehensive income or loss are reclassified to earnings when the hedged transaction affects earnings and are classified in a manner consistent with the transaction being hedged. The Company formally documents the relationships between hedging instruments and the respective hedged items, as well as its risk management objectives for hedge transactions. The Company evaluates the effectiveness of its hedging relationships both at the hedge’s inception and on an ongoing basis. Any ineffective portion of the change in fair value of a derivative instrument used as a hedge instrument in a fair value or cash flow hedge is recognized immediately in earnings. The ineffective portion is based on the extent to which exact offset is not achieved between the change in fair value of the hedge instrument and the cumulative change in expected future cash flows on the hedged transaction from inception of the hedge in a cash flow hedge or the change in the fair value. Ineffectiveness was insignificant for the periods disclosed within.
Fair Value	Fair Value Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly hypothetical transaction between market participants at a given measurement date. Valuation techniques used must maximize the use of observable inputs and minimize the use of unobservable inputs.
Income Taxes	Income Taxes Deferred income taxes are provided for temporary differences arising from differences between the financial statement and tax basis of assets and liabilities existing at each balance sheet date using enacted tax rates anticipated to be in effect when the related taxes are expected to be paid or recovered. A valuation allowance is established if it is more likely than not that a deferred tax asset will not be realized. Management reassesses the ability to realize its deferred tax assets annually in the fourth quarter or when circumstances indicate that the ability to realize deferred tax assets has changed. In determining the need for a valuation allowance, the Company considers projected realization of tax benefits based on expected levels of future taxable income, available tax planning strategies and the reversal of temporary differences. Benefits from tax positions that are uncertain are not recognized unless the Company concludes that it is more likely than not that the position would be sustained in a dispute with taxing authorities, should the dispute be taken to the court of last resort. The Company would measure any such benefit at the largest amount of benefit that is greater than 50 percent likely of being realized upon settlement with taxing authorities.
Benefit Plans	Benefit Plans The Company has non-contributory defined benefit pension plans covering most of its salaried and hourly employees. On January 1, 2015 the Company’s cash balance and excess pension plans were amended to freeze new service credits for any new or active employee. The Company also currently provides certain postretirement medical and life insurance coverage for eligible employees. The cost of providing these benefits is determined on an actuarial basis and accrued over the employee’s period of active service. The Company recognizes the overfunded or underfunded status of these plans as determined on an actuarial basis on the balance sheet and the changes in the funded status are recognized in other comprehensive income. The Company amortizes actuarial gains and losses over the remaining service attribution periods of the employees using the corridor method.
Stock-Based Compensation	Stock-Based Compensation The compensation cost of all stock-based awards is determined based on the grant-date fair value of the award, and is recognized over the requisite service period. The grant-date fair value of option awards and restricted stock awards with a market condition is determined using a Monte Carlo simulation. Compensation cost for an award with performance conditions is accrued if it is probable that the conditions will be met. The Company accounts for forfeitures as they occur.
Recently Adopted Accounting Guidance and Recent Accounting Guidance Issued Not Yet Effective	Recently Adopted Accounting Guidance In March 2016, the FASB issued Accounting Standards Update No. 2016-09, Compensation - Stock Compensation (Topic 718) ("ASU 2016-09"). ASU 2016-09 identifies areas for simplification involving several aspects of accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, an option to recognize gross stock compensation expense with actual forfeitures recognized as they occur, as well as certain classifications on the statement of cash flows. The Company adopted all provisions of this new accounting standard in the first quarter of 2017 and changed its forfeiture policy to recognize the impact of forfeitures when they occur from estimating expected forfeitures in determining stock-based compensation expense. There was no material impact to the Company's financial statements. Recent Accounting Guidance Issued Not Yet Effective In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers.” ASU 2014-09 is a comprehensive revenue recognition standard that will supersede nearly all existing revenue recognition guidance under current U.S. GAAP and replace it with a principle based approach for determining revenue recognition. ASU 2014-09 requires that companies recognize revenue based on the value of transferred goods or services as they occur in the contract. The ASU also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. ASU 2014-09 is effective for interim and annual periods beginning after December 15, 2017. The Company’s primary source of revenue is from the sale of coal through both short-term and long-term contracts with utilities, industrial customers and steel producers whereby revenue is currently recognized when risk of loss has passed to the customer. During the fourth quarter of 2017, the Company finalized its assessment related to the new standard by analyzing certain contracts representative of the majority of the Company’s coal sales and determined that the timing of revenue recognition related to the Company’s coal sales will remain consistent between the new standard and the current standard. The Company also reviewed other sources of revenue, and concluded the current basis of accounting for these items is in accordance with the new standard. The Company has concluded its adoption, using the modified retrospective method, will not have a material impact on its consolidated financial statements and there will be no cumulative adjustment to retained earnings. The Company also reviewed the disclosure requirements under the new standard and is compiling information needed for the expanded disclosures required during the first quarter of 2018. In February 2016, the FASB issued ASU No. 2016-02, “Leases” which, for operating leases, requires a lessee to recognize a right-of-use asset and a lease liability, initially measured at the present value of the lease payments, in its balance sheet. The standard also requires a lessee to recognize a single lease cost, calculated so that the cost of the lease is allocated over the term of the lease, on a generally straight line basis. The ASU is effective for public companies for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years; early adoption is permitted. The Company has both operating and capital leases. We expect the adoption of this standard to result in the recognition of right-of-use assets and lease liabilities not currently recorded on the Company’s financial statements. The Company is currently in the process of accumulating all contractual lease arrangements in order to determine the impact on its financial statements. In August 2016, the FASB issued ASU No. 2016-15, “Classification of Certain Cash Receipts and Cash Payments.” The amendment requires the classification of certain cash receipts and cash payments in the statement of cash flows to reduce diversity in practice. The new guidance will be effective for fiscal years beginning after December 15, 2017 and the interim periods therein, with early adoption permitted. The amendments in the classification should be applied retrospectively to all periods presented, unless deemed impracticable, in which case, the prospective application is permitted. The Company plans to adopt the guidance in this standard during the first quarter of 2018. In October 2016, the FASB issued ASU No. 2016-18, “Statement of Cash Flows-Restricted Cash.” The amendment requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning period and end of period total amounts shown on the statement of cash flows. ASU 2016-18 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years; early adoption is permitted. The Company plans to adopt the guidance in this standard during the first quarter of 2018. In March 2017, the FASB issued ASU No. 2017-07, “Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost.” Under the new guidance, employers will present the service cost component of the net periodic benefit cost in the same income statement line item(s) as other employee compensation costs arising from services rendered during the period. Employers will present the other components separately from the line item(s) that includes the service cost and outside of any subtotal of operating income, if one is presented. Employers will have to disclose the line(s) used to present the other components of net periodic benefit cost, if the components are not presented separately in the income statement. Additionally, only the service cost component will be eligible for capitalization in assets. ASU 2017-07 is effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal year; early adoption is permitted. The Company plans to adopt the guidance in this standard during the first quarter of 2018. In August 2017, the FASB issued ASU No. 2017-12, “Targeted Improvements to Accounting for Hedging Activities.” The new guidance provides targeted improvements to the accounting for hedging activities to better align an entity’s risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedging results. ASU 2017-12 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years; early adoption is permitted. The Company anticipates early adopting the standard in the first quarter of 2018, although we do not expect a significant impact to the Company’s financial results.

Emergence from Bankruptcy and Fresh Start Accounting (Tables)

12 Months Ended

Dec. 31, 2017

Reorganizations [Abstract]

Fresh-Start Condensed Balance Sheet



As of October 1, 2016 (In thousands)	Predecessor (a)			Effect of Plan (b)				Fresh Start Adjustments (c)				Successor
Assets
Current assets
Cash and cash equivalents	$	400,205		$	(199,718	)	(d)	$	—			$	200,487
Short term investments	111,451			—				—				111,451
Restricted cash	81,563			—				—				81,563
Trade accounts receivable	165,522			—				—				165,522
Other receivables	17,227			—				779			(j)	18,006
Inventories	159,410			—				(21,078		)	(k)	138,332
Prepaid royalties	4,805			—				—				4,805
Deferred income taxes	—			—				—				—
Coal derivative assets	2,180			—				—				2,180
Other current assets	36,960			6,367				53,851			(l)	97,178
Total current assets	979,323			(193,351		)		33,552				819,524

Property, plant and equipment, net	3,434,941			—				(2,363,829		)	(m)	1,071,112
Other assets
Prepaid royalties	20,997			—				(20,997		)	(n)	—
Equity investments	164,232			—				(61,606		)	(o)	102,626
Other noncurrent assets	58,569			34,495			(e)	37,503			(p)	130,567
Total other assets	243,798			34,495				(45,100		)		233,193
Total assets	$	4,658,062		$	(158,856	)		$	(2,375,377	)		$	2,123,829

Liabilities and Stockholders’ Equity (Deficit)
Liabilities not subject to compromise
Accounts payable	$	74,595		$	—			$	(250	)	(q)	$	74,345
Accrued expenses and other current liabilities	225,739			(36,331		)	(f)	26,644			(r)	216,052
Current maturities of debt	3,397			3,265			(g)	—				6,662
Total current liabilities	303,731			(33,066		)		26,394				297,059
Long-term debt	30,037			323,235			(g)	—				353,272
Asset retirement obligations	394,699			—				(60,570		)	(s)	334,129
Accrued pension benefits	23,716			—				24,565			(t)	48,281
Accrued other postretirement benefits	87,123			—				24,836			(t)	111,959
Accrued workers’ compensation	119,828			—				74,520			(u)	194,348
Deferred income taxes	—			—				—				—
Other noncurrent liabilities	96,410			—				888			(v)	97,298
Total liabilities not subject to compromise	1,055,544			290,169				90,633				1,436,346

Liabilities subject to compromise	5,278,612			(5,278,612		)	(h)	—				—

Total liabilities	6,334,156			(4,988,443		)		90,633				1,436,346

Stockholders’ equity (deficit)
Common stock, predecessor	2,145			(2,145		)	(i)	—				—
Common stock, successor	—			250			(b)	—				250
Paid-in capital, predecessor	3,056,307			(3,056,307		)	(i)	—				—
Paid-in capital, successor	—			687,233			(b)	—				687,233
Treasury stock, at cost	(53,863		)	53,863			(i)	—				—
Accumulated earnings (deficit)	(4,678,977		)	7,146,693			(i)	(2,467,716		)		—
Accumulated other comprehensive income (loss)	(1,706		)	—				1,706				—
Total stockholders’ equity (deficit)	(1,676,094		)	4,829,587				(2,466,010		)		687,483
Total liabilities and stockholders’ equity (deficit)	$	4,658,062		$	(158,856	)		$	(2,375,377	)		$	2,123,829


(a)	Represents the Predecessor consolidated balance sheet as of October 1, 2016.


(b)	Represents amounts recorded for the implementation of the Plan on the Effective Date. This includes the settlement of liabilities subject to compromise through a combination of cash payments, the issuance of new common stock and warrants and the issuance of new debt. The following is the calculation of the total pre-tax gain on the settlement of the liabilities subject to compromise:



	In thousands
Liabilities subject to compromise	$	5,278,612
Less amounts issued to settle claims:
Common stock (at par) Successor	(250		)
Warrants Successor	(14,822		)
Paid-in capital Successor	(672,411		)
Issuance of Term Loan Successor	(326,500		)
Cash payment to settle claims and professional fees	(122,525		)

Total pre-tax gain on plan effects	$	4,142,104


(c)	Represents the fresh start accounting adjustments required to record the assets and liabilities of the Company at fair value.


(d)	The following table reflects the use of cash at emergence:



	In thousands
Payment to secured lenders	$	43,496
Payments to unsecured creditors	42,399
Final adequate protection payment	36,331
Collateral requirements	31,665
Professional fees	31,630
Other	14,197

Total cash outflow at emergence	$	199,718


(e)	Represents amounts paid for required collateral deposits.


(f)	Represents the final adequate protection payments made to the secured lenders.


(g)	Represents the fair value of the $326.5 million new term loan of which $3.3 million is shown within current maturities of debt.


(h)	Liabilities subject to compromise include unsecured or under-secured liabilities incurred prior to the Chapter 11 filing; and consists of the following:



Previously Reported Balance Sheet Line	In thousands
Debt	$	5,026,806
Accrued expenses and other current liabilities	136,295
Accounts payable	106,297
Other noncurrent liabilities	9,214

Total liabilities subject to compromise	$	5,278,612


(i)	Reflects the impacts of the reorganization adjustments:



	In thousands
Total pre-tax gain on settlement of claims	$	4,142,104
Cancellation of predecessor common stock	2,145
Cancellation of predecessor paid-in capital	3,056,307
Cancellation of predecessor treasury stock	(53,863		)

Net impact on accumulated earnings (deficit)	$	7,146,693


(j)	Represents adjustments to record other receivables at fair value which includes an $0.8 million short-term receivable related to insurance coverage for self-insured workers’ compensation obligations.

(k)


(l)	Represents the short-term portion of above market coal sales contracts of $71.1 million offset by $11.3 million in reductions related to prepaid balances. The fair value of sales contracts was estimated using a discounted cash flow model and will be amortized into earnings as the coal is shipped throughout the term of the associated contracts.


(m)	Represents a $2.4 billion reduction in property, plant and equipment to estimated fair value as discussed below:



	Predecessor		Fresh Start Adjustments			Successor
(in thousands)
Net Coal Properties	$	2,358,779	$	(1,971,314	)	$	387,465
Net Plant & Equipment	812,888		(405,259		)	407,629
Net Deferred Charges	263,274		12,744			276,018

	$	3,434,941	$	(2,363,829	)	$	1,071,112

The fair value of deferred charges represents the corresponding asset related to the asset retirement obligation discussed in item (q) below.


(n)	Represents a fair value adjustment to a long-term prepaid royalty balance that the Company has concluded should not be assigned value based on market conditions and after considering economic obsolescence.

(o)

(p)


(q)	Represents a fair value adjustment to miscellaneous accounts payable.

(r)


(s)	Represents the fair value adjustment related to the Company’s asset retirement obligations which was calculated using discounted cash flow models based on current mine plans using the guidance provided within Accounting Standard Codification 410-20, “Asset Retirement Obligations.” The discount rates ranged from 7.06% to 9.08%.


(t)	Pension and postretirement benefits were fair valued based on plan assets and employee benefit obligations at October 1, 2016. The benefit obligations were computed using the applicable October 1, 2016 discount rates. In conjunction with fresh start accounting, the Company updated its mortality rate table assumptions and corridor assumption.

(u)

(v)

Schedule of Reorganization Items, Net

The Company’s reorganization items, net for the respective periods are as follows:



	Successor						Predecessor
	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016			Year Ended December 31, 2015
(In thousands)
Gain on settlement of claims (per above)	$	—		$	—		$	4,142,104		$	—
Fresh start adjustments, net (per above)	—			—			(2,466,010		)	—
Professional fees	(2,398		)	(759		)	(46,053		)	—

	$	(2,398	)	$	(759	)	$	1,630,041		$	—

Accumulated Other Comprehensive Income (Loss) (Tables)

12 Months Ended

Dec. 31, 2017

Accumulated Other Comprehensive Income (Loss) [Abstract]

Schedule of Accumulated Other Comprehensive Income (Loss)

The following items are included in accumulated other comprehensive income (loss):




				Pension,
				Postretirement						Accumulated
				and Other Post-						Other
	Derivative			Employment			Available-for-			Comprehensive
	Instruments			Benefits			Sale Securities			Income (Loss)
	(In thousands)
Predecessor Company
January 1, 2016	$	325		$	(721	)	$	(1,419	)	$	(1,815	)
Unrealized gains (losses)	(138		)	—			701			563
Amounts reclassified from accumulated other comprehensive income (loss)	(316		)	(1,363		)	1,225			(454		)
Fresh start accounting adjustment	129			2,084			(507		)	1,706
October 1, 2016	—			—			—			—
Successor Company
Unrealized gains (losses)	—			24,067			387			24,454
Amounts reclassified from accumulated other comprehensive income (loss)	—			—			—			—
December 31, 2016	$	—		$	24,067		$	387		$	24,454
Unrealized gains (losses)	497			(3,589		)	—			(3,092		)
Amounts reclassified from accumulated other comprehensive income (loss)	150			(758		)	(387		)	(995		)
December 31, 2017	$	647		$	19,720		$	—		$	20,367

Schedule of comprehensive income reclassifications

The following amounts were reclassified out of accumulated other comprehensive income (loss) during the respective periods:



Details about accumulated other comprehensive income components	Successor					Predecessor			Line Item in the Consolidated Statement of Operations
	Year Ended December 31, 2017			October 2 through December 31, 2016		January 1 through October 1, 2016
(in thousands)
Derivative instruments
Coal hedges	$	—		$	—	$	397		Revenues
Interest rate hedges	(150		)			—			Interest expense
	—			—		(81		)	Provision for (benefit from) income taxes
	$	(150	)	$	—	$	316		Net of tax

Pension, postretirement and other post-employment benefits
Amortization of prior service credits ¹	$	—		$	—	$	7,854
Amortization of net actuarial gains (losses) ¹	—			—		(6,010		)
Curtailments	(773		)	—		—
Settlements	1,531			—		—
	758			—		1,844			Total before tax
	—			—		(481		)	Provision for (benefit from) income taxes
	$	758		$	—	$	1,363		Net of tax

Available-for-sale securities ²	$	387		$	—	$	(2,263	)	Interest and investment income
	—			—		1,038			Provision for (benefit from) income taxes
	$	387		$	—	$	(1,225	)	Net of tax
¹ Production-related benefits and workers’ compensation costs are included in costs to produce coal.
² The gains and losses on sales of available-for-sale-securities are determined on a specific identification basis.

Impairment Charges and Mine Closure Costs (Tables)

12 Months Ended

Dec. 31, 2017

Impairment Charges and Mine Closure Costs [Abstract]

Restructuring and Related Costs

The following table summarizes the amounts reflected on the line “Asset impairment and mine closure costs” in the consolidated statements of operations:



	Successor				Predecessor
Description	Year Ended December 31, 2017		October 2 through December 31, 2016		January 1 through October 1, 2016		Year Ended December 31, 2015
(In thousands)
Coal lands and mineral rights	$	—	$	—	$	74,144	$	2,210,488
Plant and equipment	—		—		—		199,107
Deferred development	—		—		—		159,474
Prepaid royalties	—		—		3,406		41,990
Equity investments	—		—		40,920		21,325
Inventories	—		—		—		66
Other	—		—		10,797		(4,147		)
Total	$	—	$	—	$	129,267	$	2,628,303

Inventories (Tables)

12 Months Ended

Dec. 31, 2017

Inventory Disclosure [Abstract]

Inventories

Inventories consist of the following:



	December 31, 2017		December 31, 2016
(In thousands)
Coal	$	54,692	$	37,268
Repair parts and supplies	74,268		76,194
	$	128,960	$	113,462

Investments in Available-for-Sale Securities (Tables)

12 Months Ended

Dec. 31, 2017

Available-for-sale Securities [Abstract]

Available-for-sale Securities

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



	December 31, 2017
										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	$	64,151	$	22	$	(73	)	$	64,100	$	64,100	$	—
Corporate notes and bonds	92,038		—		(292		)	91,746		91,746		—
Total Investments	$	156,189	$	22	$	(365	)	$	155,846	$	155,846	$	—



	December 31, 2016
										Balance Sheet
			Gross		Gross					Classification
			Unrealized		Unrealized			Fair		Short-Term		Other
	Cost Basis		Gains		Losses			Value		Investments		Assets
	(In thousands)
Available-for-sale:
Corporate notes and bonds	$	88,161	$	—	$	(89	)	$	88,072	$	88,072	$	—
Equity securities	1,749		388		—			2,137		—		2,137
Total Investments	$	89,910	$	388	$	(89	)	$	90,209	$	88,072	$	2,137

- 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 Method Investments and Membership Interests in Joint Ventures (Tables)

12 Months Ended

Dec. 31, 2017

Equity Method Investments and Joint Ventures [Abstract]

Schedule Of Equity Method Investments

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



(In thousands)	Knight Hawk			DTA			Millennium			Tongue River			Other			Total
Predecessor Company
January 1, 2015	$	158,477		$	13,738		$	40,223		$	20,740		$	2,664		$	235,842
Advances to (distributions from) affiliates, net	(29,862		)	3,207			7,052			913			330			(18,360		)
Equity in comprehensive income (loss)	22,977			(3,706		)	(9,686		)	(328		)	(1,278		)	7,979
Impairment of equity investment	—			—			—			(21,325		)	—			(21,325		)
Sale of equity investment	—			—			—			—			(2,259		)	(2,259		)
December 31, 2015	151,592			13,239			37,589			—			(543		)	201,877
Advances to (distributions from) affiliates, net	(8,374		)	1,474			1,966			—			—			(4,934		)
Equity in comprehensive income (loss)	9,033			(2,095		)	(1,530		)	—			(94		)	5,314
Impairment of equity investment	—			—			(38,025		)	—			—			(38,025		)
Fresh start accounting adjustment	(58,251		)	(4,018		)	—			—			662			(61,607		)
October 1, 2016	94,000			8,600			—			—			25			102,625
Successor Company
Advances to (distributions from) affiliates, net	(9,076		)	822			—			—			—			(8,254		)
Equity in comprehensive income (loss)	2,569			(841		)	—			—			(25		)	1,703
December 31, 2016	$	87,493		$	8,581		$	—		$	—		$	—		$	96,074
Investments in affiliates	—			7,158			—			—			—			7,158
Advances to (distributions from) affiliates, net	(8,736		)	3,014			—			—			—			(5,722		)
Equity in comprehensive income (loss)	11,409			(2,812		)	—			—			—			8,597

December 31, 2017	$	90,166		$	15,941		$	—		$	—		$	—		$	106,107

Sales Contracts (Tables)

12 Months Ended

Dec. 31, 2017

Acquired Sales Contracts [Abstract]

Schedule of Sales Contracts

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



	December 31, 2017								December 31, 2016
	Assets			Liabilities			Net Total		Assets			Liabilities			Net Total
	(In thousands)								(In thousands)
Original fair value	$	97,196		$	31,742				$	97,196		$	31,742
Accumulated amortization	(84,760		)	(29,979		)			(25,625		)	(24,829		)
Total	$	12,436		$	1,763		$	10,673	$	71,571		$	6,913		$	64,658
Balance Sheet classification:
Other current	$	12,432		$	934				$	59,702		$	5,114
Other noncurrent	$	4		$	829				$	11,869		$	1,799

Derivatives (Tables)

12 Months Ended

Dec. 31, 2017

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Price Risk Derivatives

At December 31, 2017, the Company held derivatives for risk management purposes that are expected to settle in the following years:



(Tons in thousands)	2018	2019	Total
Coal sales	1,706	159	1,865
Coal purchases	747	—	747

Disclosure Of Fair Value Of Derivatives

The fair value and location of derivatives reflected in the accompanying consolidated balance sheets are as follows:



	December 31, 2017									December 31, 2016
Fair Value of Derivatives	Asset			Liability						Asset			Liability
(In thousands)	Derivative			Derivative						Derivative			Derivative
Derivatives Designated as Hedging Instruments
Coal	$	942		$	(2,146	)				$	—		$	(15	)

Derivatives Not Designated as Hedging Instruments
Heating oil -- diesel purchases	5,354			—						4,646			—
Coal held for trading purposes, exchange traded swaps and futures	44,088			(45,221		)				68,948			(68,740		)
Coal -- risk management	5,139			(9,892		)				475			(580		)
Natural gas	27			—						86			(13		)
Total	54,608			(55,113		)				74,155			(69,333		)
Total derivatives	55,550			(57,259		)				74,155			(69,348		)
Effect of counterparty netting	(50,042		)	50,042						(69,247		)	69,247
Net derivatives as classified in the balance sheets	$	5,508		$	(7,217	)	$	(1,709	)	$	4,908		$	(101	)	$	4,807



		December 31, 2017			December 31, 2016
Net derivatives as reflected on the balance sheets
Heating oil	Other current assets	$	5,354		$	4,646
Coal	Other current assets	154			262
	Accrued expenses and other current liabilities	(7,217		)	(101		)
		$	(1,709	)	$	4,807

Effects Of Derivatives On Measures Of Financial Performance

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

Derivatives used in Cash Flow Hedging Relationships (in thousands)

For the noted periods,



		Gain (Loss) Recognized in Other Comprehensive Income (Effective Portion)
		Successor					Predecessor
		Year Ended December 31, 2017			October 2 through December 31, 2016		January 1 through October 1, 2016			Year Ended December 31, 2015
Coal sales	⁽¹⁾	$	(2,127	)	$	—	$	(672	)	12,816
Coal purchases	⁽²⁾	942			—		536			(6,718		)
		$	(1,185	)	$	—	$	(136	)	$	6,098


		Gains (Losses) Reclassified from Other Comprehensive Income into Income (Effective Portion)
		Successor					Predecessor
		Year Ended December 31, 2017			October 2 through December 31, 2016		January 1 through October 1, 2016			Year Ended December 31, 2015
Coal sales		$	—		$	—	$	1,634		$	18,635
Coal purchases		—			—		(1,237		)	(9,060		)
		$	—		$	—	$	397		$	9,575

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 respective periods.

Derivatives Not Designated as Hedging Instruments (in thousands)

For the noted periods,



		Gain (Loss) Recognized
		Successor						Predecessor
		Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016			Year Ended December 31, 2015
Coal — unrealized	⁽³⁾	$	(4,648	)	$	(408	)	$	(1,662	)	$	(3,883	)
Coal — realized	⁽⁴⁾	$	—		$	116		$	(476	)	$	3,236
Heating oil — diesel purchases	⁽⁴⁾	$	(1,057	)	$	827		$	826		$	(8,294	)
Natural gas		$	(774	)	$	(91	)	$	(463	)	$	878
Foreign currency		$	—		$	(9	)	$	(451	)	$	(867	)

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

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2017

Accrued Expenses and Other Current Liabilities [Abstract]

Schedule of Accrued Liabilities

Accrued expenses and other current liabilities consist of the following:



	December 31, 2017		December 31, 2016
(In thousands)
Payroll and employee benefits	$	53,149	$	58,468
Taxes other than income taxes	77,017		92,733
Interest	246		8,032
Sales contracts	934		5,114
Workers’ compensation	18,782		15,184
Asset retirement obligations	19,840		19,515
Other	14,193		6,194
	$	184,161	$	205,240

Debt and Financing Arrangements (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Debt



	December 31, 2017			December 31, 2016
(In thousands)
Term loan due 2024 ($297.8 million face value)	$	296,435		$	—
Term loan due 2021 ($325.7 million face value)	$	—		$	325,684
Other	36,514			37,195
Debt issuance costs	(7,032		)	—
	325,917			362,879
Less current maturities of debt	15,783			11,038
Long-term debt	$	310,134		$	351,841

Schedule of Interest Rate Swap Agreements

Below is a summary of the Company’s outstanding interest rate swap agreements designated as hedges as of

December 31, 2017:



Notional Amount (in millions)	Effective Date	Fixed Rate	Receive Rate	Expiration Date

$250.0	June 30, 2017	1.372%	1-month LIBOR	June 29, 2018
$250.0	June 29, 2018	1.662%	1-month LIBOR	June 28, 2019
$200.0	June 28, 2019	1.952%	1-month LIBOR	June 30, 2020
$150.0	June 30, 2020	2.182%	1-month LIBOR	June 30, 2021

Schedule of Maturities of Long-term Debt

The contractual maturities of debt as of December 31, 2017 are as follows:



Year	(In thousands)
2018	$	16,809
2019	11,119
2020	11,442
2021	8,853
2022	3,130
Thereafter	282,911
	$	334,264

Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of Components of Income Tax Expense (Benefit)

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



	Successor						Predecessor
	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016			Year Ended December 31, 2015
(In thousands)
Current:
Federal	$	835		$	—		$	—		$	—
State	31			(252		)	7			3
Total current	866			(252		)	7			3
Deferred:
Federal	(36,162		)	1,352			(4,720		)	(329,393		)
State	41			56			87			(43,990		)
Total deferred	(36,121		)	1,408			(4,633		)	(373,383		)
	$	(35,255	)	$	1,156		$	(4,626	)	$	(373,380	)

Schedule of Effective Income Tax Rate Reconciliation

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



	Successor						Predecessor
	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016			Year Ended December 31, 2015
(In thousands)
Income tax provision (benefit) at statutory rate	$	71,118		$	12,112		$	433,109		$	(1,150,283	)
Percentage depletion allowance	(31,255		)	(4,292		)	(3,681		)	(19,035		)
State taxes, net of effect of federal taxes	7,002			633			(46,122		)	(76,445		)
Reversal of cancellation of indebtedness income	—			—			(1,493,162		)	—
Worthless stock deduction	—			—			(80,077		)	—
Change in valuation allowance	(410,983		)	(7,655		)	1,185,326			865,146
Impact of Tax Cuts and Jobs Act of 2017	332,345			—			—			—
Other, net	(3,482		)	358			(19		)	7,237
	$	(35,255	)	$	1,156		$	(4,626	)	$	(373,380	)

Schedule of Deferred Tax Assets and Liabilities



	December 31, 2017			December 31, 2016
(In thousands)
Deferred tax assets:
Tax loss carryforwards	$	271,405		$	376,293
Tax credit carryforwards	29,736			22,798
Investment in tax partnerships & corporations	308,653			604,914
Other	28,321			39,251
Gross deferred tax assets	638,115			1,043,256
Valuation allowance	(610,571		)	(1,021,553		)
Total deferred tax assets	27,544			21,703
Deferred tax liabilities:
Plant and equipment	3,674			7,332
Other	1,351			14,258
Total deferred tax liabilities	5,025			21,590
Net deferred tax asset	22,519			113

Summary of Income Tax Contingencies

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



		(In thousands)
Balance at	January 1, 2015	$	34,709
Additions based on tax positions related to the current year		4,168
Balance at	December 31, 2015	38,877
Additions based on tax positions related to the current year		2,979
Additions for tax positions of prior years		2,709
Reductions as a result of lapses in the statute of limitations		(37,110		)
Balance at	December 31, 2016	7,455
Additions for tax positions of prior years		—
Additions for tax positions related to the current year		3,928
Reductions as a result of bankruptcy		—
Balance at	December 31, 2017	$	11,383

Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2017

Asset Retirement Obligation [Abstract]

Schedule of Change in Asset Retirement Obligation

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



	Successor						Predecessor
	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016
(In thousands)
Balance at beginning of period (including current portion)	$	356,742		$	354,326		$	410,454
Accretion expense	30,209			7,634			24,321
Obligations of divested operations	(12,569		)	—			(14,702		)
Adjustments to the liability from changes in estimates	(23,215		)	—			3,003
Liabilities settled	(22,472		)	(5,218		)	(11,087		)
Fresh start accounting adjustment	—			—			(57,663		)
Balance at period end	$	328,695		$	356,742		$	354,326
Current portion included in accrued expenses	(19,840		)	(19,515		)	(17,290		)
Noncurrent liability	$	308,855		$	337,227		$	337,036

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Summary Of Financial Assets And Liabilities Accounted For At Fair Value

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



	Fair Value at				December 31, 2017
	Total		Level 1			Level 2		Level 3
	(In thousands)
Assets:
Investments in marketable securities	$	155,846	$	64,100		$	91,746	$	—
Derivatives	7,339		—			1,985		5,354
Total assets	$	163,185	$	64,100		$	93,731	$	5,354
Liabilities:
Derivatives	$	7,217	$	7,263		$	26	$	(72	)



	Fair Value at					December 31, 2016
	Total		Level 1				Level 2		Level 3
	(In thousands)
Assets:
Investments in marketable securities	$	90,209	$	2,137			$	88,072	$	—
Derivatives	4,908		262				—		4,646
Total assets	$	95,117	$	2,399			$	88,072	$	4,646
Liabilities:
Derivatives	$	101	$	(8	)		$	—	$	109

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.



	Successor						Predecessor
	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016
(In thousands)
Balance, beginning of period	$	4,537		$	3,842		$	2,432
Realized and unrealized (gains) losses recognized in earnings, net	(2,305		)	926			(1,686		)
Included in other comprehensive income	—			—			—
Purchases	4,910			1,225			5,021
Issuances	(535		)	(34		)	(488		)
Settlements	(1,181		)	(1,422		)	(1,437		)
Ending balance	$	5,426		$	4,537		$	3,842

Capital Stock Capital Stock (Tables)

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Dividends declared and paid

The Company declared and paid cash dividends per share during the periods presented below:



2017:	Dividends per share		Amount (in thousands)
1st quarter	$	—	$	—
2nd quarter	0.35		8,563
3rd quarter	0.35		8,200
4th quarter	0.35		7,606
Total cash dividends declared and paid	$	1.05	$	24,369

Share repurchase activity

Below is a table showing the share repurchase activity in 2017:



2017:	Number of Shares	Average Repurchase Price per Share		Amount (in thousands)
1st quarter	—	$	—	$	—
2nd quarter	710,701	$	71.82	51,043
3rd quarter	2,208,133	$	75.49	166,685
4th quarter	1,058,381	$	79.73	84,381
Total shares repurchased	3,977,215	$	75.96	$	302,109

Stock-Based Compensation and Other Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2017

Share-based Compensation [Abstract]

Schedule of Restricted Stock Units Activity

Information regarding the restricted stock units activity and weighted average grant-date fair value follows:



	Time Based Awards				Performance Based Awards
	Restricted Stock Units		Weighted Average Grant-Date Fair Value		Restricted Stock Units	Weighted Average Grant-Date Fair Value
(Shares in thousands)
Outstanding at January 1, 2017	159		$	78.60	225	$	67.34
Granted	92		81.91		86	101.38
Forfeited/Canceled	(2	)	78.60		—	—
Vested	(9	)	78.60		—	—
Unvested outstanding at December 31, 2017	240		$	79.87	311	$	76.75

Workers' Compensation Expense (Tables)

12 Months Ended

Dec. 31, 2017

Workers' compensation expense

Workers’ compensation expense consists of the following components:



	Successor				Predecessor
	Year Ended December 31, 2017		October 2 through December 31, 2016		January 1 through October 1, 2016		Year Ended December 31, 2015
(In thousands)
Self-insured occupational disease benefits:
Service cost	$	6,320	$	1,583	$	3,465	$	4,282
Interest cost	4,651		1,126		3,184		3,944
Net amortization	—		—		4,325		6,973
Total occupational disease	$	10,971	$	2,709	$	10,974	$	15,199
Traumatic injury claims and assessments	3,208		3,162		6,628		16,781
Total workers’ compensation expense	$	14,179	$	5,871	$	17,602	$	31,980

Schedule of Changes in Occupational Disease Obligations

The table below reconciles changes in the occupational disease liability for the respective period.



	Successor						Predecessor
(In thousands)	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016
Beginning of period	$	111,159		$	119,710		$	90,836
Service cost	6,320			1,583			3,465
Interest cost	4,651			1,126			3,184
Curtailments	(5,433		)	—			4,156
Actuarial (gain) loss	12,242			(9,675		)	—
Benefit and administrative payments	(6,513		)	(1,585		)	(3,728		)
Fresh start accounting adjustment	—			—			21,797
	$	122,426		$	111,159		$	119,710

Schedule of Occupational Disease Obligation Assumptions Used

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



	Successor		Predecessor
	Year Ended December 31, 2017	October 2 through December 31, 2016	January 1 through October 1, 2016
(Percentages)
Occupational Disease Benefit
Discount rate	3.66	4.31	3.80
Cost escalation rate	N/A	N/A	N/A

Workers' compensation liabilities

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



	Year Ended December 31, 2017		Year Ended December 31, 2016
(In thousands)
Occupational disease costs	$	122,426	$	111,159
Traumatic and other workers’ compensation claims	81,191		88,593
Total obligations	203,617		199,752
Less amount included in accrued expenses	18,782		15,184
Noncurrent obligations	$	184,835	$	184,568

Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2017

Pension and Other Postretirement Benefits Cost (Reversal of Cost) [Abstract]

Pension Benefit Costs

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



	Pension Benefits									Other Postretirement Benefits
	Successor						Predecessor			Successor						Predecessor
	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016			Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016
(In thousands)
CHANGE IN BENEFIT OBLIGATIONS
Benefit obligations at beginning of period	$	313,629		$	341,427		$	301,292		$	111,867		$	120,311		$	103,460
Service cost	—			—			—			671			180			393
Interest cost	11,169			2,768			9,338			4,150			978			3,223
Divestitures (see Note 5 to the Consolidated Financial Statements)	(29,097		)	—			—			—			—			—
Settlements	(1,532		)	(135		)	—			—			—			—
Curtailments	—			—			454			(520		)	—			714
Benefits paid	(38,197		)	(11,009		)	(8,699		)	(8,152		)	(1,962		)	(8,273		)
Other-primarily actuarial (gain) loss	14,126			(19,422		)	—			2,503			(7,640		)	—
Fresh start accounting adjustments	—			—			39,042			—			—			$	20,794
Benefit obligations at end of period	$	270,098		$	313,629		$	341,427		$	110,519		$	111,867		$	120,311
CHANGE IN PLAN ASSETS
Value of plan assets at beginning of period	$	274,225		$	292,726		$	273,499		$	—		$	—		$	—
Actual return on plan assets	39,689			(7,899		)	27,811						—			—
Employer contributions	429			407			115			8,152			1,962			8,273
Benefits paid	(38,197		)	(11,009		)	(8,699		)	(8,152		)	(1,962		)	(8,273		)
Divestitures	$	(20,504	)	$	—		$	—		$	—		$	—		$	—
Value of plan assets at end of period	$	255,642		$	274,225		$	292,726		$	—		$	—		$	—
Accrued benefit cost	$	(14,456	)	$	(39,404	)	$	(48,701	)	$	(110,519	)	$	(111,867	)	$	(120,311	)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit (cost)	$	—		$	—		$	—		$	—		$	—		$	—
Accumulated gain	16,178			6,751			—			5,137			7,640			—
	$	16,178		$	6,751		$	—		$	5,137		$	7,640		$	—
BALANCE SHEET AMOUNTS
Current liability	$	(420	)	$	(520	)	$	(420	)	$	(8,150	)	$	(10,422	)	$	(8,352	)
Noncurrent liability	(14,036		)	(38,884		)	(48,281		)	(102,369		)	(101,445		)	(111,959		)
	$	(14,456	)	$	(39,404	)	$	(48,701	)	$	(110,519	)	$	(111,867	)	$	(120,311	)

Other Postretirement Benefit Costs

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



	Pension Benefits												Other Postretirement Benefits
	Successor						Predecessor						Successor					Predecessor
	Year Ended December 31, 2017			October 2 through December 31, 2016			January 1 through October 1, 2016			Year Ended December 31, 2015			Year Ended December 31, 2017			October 2 through December 31, 2016		January 1 through October 1, 2016			Year Ended December 31, 2015
(In thousands)
Service cost	$	—		$	—		$	—		$	9		$	671		$	180	$	393		$	866
Interest cost	11,169			2,768			9,338			14,604			4,150			978		3,223			1,904
Curtailments	—			—			454			—			(520		)	—		(970		)	—
Settlements	(1,532		)	(135		)	—			2,656			—			—		—			—
Expected return on plan assets	(16,498		)	(4,770		)	(13,623		)	(20,367		)	—			—		—			—
Amortization of prior service credits	—			—			—			—			—			—		(7,854		)	(8,335		)
Amortization of other actuarial losses (gains)	—			—			3,973			8,850			—			—		(849		)	(2,109		)
Net benefit cost (credit)	$	(6,861	)	$	(2,137	)	$	142		$	5,752		$	4,301		$	1,158	$	(6,057	)	$	(7,674	)

Schedule of Assumptions Used

The following table provides the weighted average assumptions used to determine the actuarial present value of projected benefit obligations for the respective periods.



	Successor		Predecessor
	Year Ended December 31, 2017	October 2 through December 31, 2016	January 1 through October 1, 2016
(Percentages)
Pension Benefits
Discount rate	3.49/3.27	3.95	3.39
Rate of compensation increase	N/A	N/A	N/A

Other Postretirement Benefits
Discount rate	3.49	3.93	3.37
Rate of compensation increase	N/A	N/A	N/A

The following table provides the weighted average assumptions used to determine net periodic benefit cost for the respective periods.



	Successor		Predecessor
	Year Ended December 31, 2017	October 2 through December 31, 2016	January 1 through October 1, 2016	Year Ended December 31, 2015
(Percentages)
Pension Benefits
Discount rate	3.77	3.39/3.95	4.59/3.80	4.15/4.61/4.41/4.60
Rate of compensation increase	N/A	N/A	N/A	N/A
Expected return on plan assets	6.20	6.85	6.85	7.00

Other Postretirement Benefits
Discount rate	3.85	3.37	4.57/3.80	3.91
Rate of compensation increase	N/A	N/A	N/A	N/A
Expected return on plan assets	N/A	N/A	N/A	N/A

Schedule of Allocation of Plan Assets

The Company’s pension plan assets at December 31, 2017 and 2016, respectively, are categorized below according to the fair value hierarchy as defined in Note 17, “Fair Value Measurements”:



	Total						Level 1				Level 2				Level 3
	2017			2016			2017		2016		2017		2016		2017		2016
	(In thousands)
Equity Securities:^(A)
U.S. small-cap	$	5,064		$	13,520		$	5,064	$	13,520	$	—	$	—	$	—	$	—
U.S. mid-cap	22,640			29,687			6,017		9,422		16,623		20,265		—		—
U.S. large-cap	43,232			70,226			21,416		34,107		21,816		36,119		—		—
Non-U.S.	10,115			18,937			—		—		10,115		18,937		—		—
Fixed income securities:																	—
U.S. government securities^(B)	66,922			26,519			60,286		19,973		6,636		6,546		—		—
Non-U.S. government securities^(C)	4,050			1,567			—		—		4,050		1,567		—		—
U.S. government asset and mortgage backed securities^(D)	2,440			1,074			—		—		2,440		1,074		—		—
Corporate fixed income^(E)	54,679			58,191			—		—		54,679		58,191		—		—
State and local government securities^(F)	3,829			6,406			—		—		3,829		6,406		—		—
Other investments^(I)	27,057			26,151			—		—		8,457		6,910		18,600		19,241
Total	$	240,028		$	252,278		$	92,783	$	77,022	$	128,645	$	156,015	$	18,600	$	19,241
Other fixed income^(G)	16,646			35,519
Short-term investments^(H)	8,573			8,598
Other liabilities^(J)	(9,605		)	(22,170		)
	$	255,642		$	274,225

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

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

^(J)Net payable amount due for pending securities purchased and sold due to broker/dealer.

Schedule of Expected Benefit Payments

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



			Other
	Pension		Postretirement
	Benefits		Benefits
	(In thousands)
2018	$	17,614	$	12,381
2019	17,834		12,549
2020	18,174		12,990
2021	18,635		13,239
2022	19,235		13,423
Next 5 years	83,071		62,854
	$	174,563	$	127,436

Earnings (Loss) Per Common Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Schedule of Weighted Average Number of Shares

The following table provides the basis for basic and diluted EPS by reconciling the numerators and denominators of the computations:



	Successor		Predecessor
	Year Ended December 31, 2017	October 2 through December 31, 2016	January 1 through October 1, 2016	Year Ended December 31, 2015
(In Thousands)
Weighted average shares outstanding:
Basic weighted average shares outstanding	23,725	25,002	21,293	21,285
Effect of dilutive securities	515	467	20	—

Diluted weighted average shares outstanding	24,240	25,469	21,313	21,285

Leases (Tables)

12 Months Ended

Dec. 31, 2017

Leases [Abstract]

Operating Leases of Lessee Disclosure

Minimum payments due in future years under these agreements in effect at December 31, 2017 are as follows:



	Operating
	Leases		Royalties
	(In thousands)
2018	$	5,936	$	3,582
2019	4,655		5,926
2020	2,260		6,953
2021	1,985		7,216
2022	2,024		7,003
Thereafter	8,292		34,371
	$	25,152	$	65,051

Risk Concentrations (Tables)

12 Months Ended

Dec. 31, 2017

Risks Concentrations [Abstract]

Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas

The Company’s foreign revenues by geographical location are as follows:



	Successor				Predecessor
	Year Ended December 31, 2017		October 2 through December 31, 2016		January 1 through October 1, 2016		Year Ended December 31, 2015
(In thousands)
Europe	$	388,926	$	61,408	$	113,888	$	170,314
Asia	264,503		55,634		68,536		96,523
North America	88,145		43,831		56,594		40,315
Central and South America	30,982		13,224		41,861		55,323
Africa	14,901		—		—		—
Brokered Sales	6,137		—		—		32,848
Total	$	793,594	$	174,097	$	280,879	$	395,323

Segment Information (Tables)

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Schedule Of Operating Segment Results



(In thousands)		PRB		MET		Other Thermal		Corporate, Other and Eliminations			Consolidated
Successor Year Ended	December 31, 2017
Revenues		$	1,024,197	$	887,839	$	396,504	$	16,083		$2,324,623
Adjusted EBITDAR		158,882		243,616		102,006		(86,747		)	417,757
Depreciation, depletion and amortization		36,349		70,896		13,588		1,631			122,464
Accretion on asset retirement obligation		20,160		2,000		2,161		5,888			30,209
Total Assets		390,665		548,476		134,397		906,094			1,979,632
Capital expenditures		6,212		32,678		11,901		8,414			59,205
Successor Period	October 2 through December 31, 2016
Revenues		$	275,703	$	200,377	$	97,382	$	2,226		$575,688
Adjusted EBITDAR		55,765		30,819		31,159		(23,246		)	94,497
Depreciation, depletion and amortization		9,949		18,287		3,911		457			32,604
Accretion on asset retirement obligation		5,049		528		540		1,517			7,634
Total assets		446,775		576,793		129,602		983,427			2,136,597
Capital expenditures		934		13,329		684		267			15,214
Predecessor Period	January 1 through October 1, 2016
Revenues		$	726,747	$	437,069	$	213,052	$	21,841		$1,398,709
Adjusted EBITDAR		113,185		11,851		31,448		(69,181		)	87,303
Depreciation, depletion and amortization		100,151		55,311		32,310		3,809			191,581
Accretion on asset retirement obligation		16,940		1,765		1,988		3,628			24,321
Total assets		456,711		619,154		131,173		916,791			2,123,829
Capital expenditures		612		17,296		3,895		60,631			82,434
Predecessor Year Ended	December 31, 2015
Revenues		$	1,448,440	$	637,941	$	428,809	$	58,070		$	2,573,260
Adjusted EBITDAR		281,039		70,450		42,734		(110,426		)	283,797
Depreciation, depletion and amortization		176,257		133,463		47,786		21,839			379,345
Accretion on asset retirement obligation		22,156		2,267		2,658		6,599			33,680
Total assets		1,648,916		772,439		366,610		2,253,916			5,041,881
Capital expenditures		21,228		24,787		11,277		61,732			119,024

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

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



	Successor					Predecessor
(In thousands)	Year Ended December 31, 2017			October 2 through December 31, 2016		January 1 through October 1, 2016			Year Ended December 31, 2015

Income (loss) before income taxes	$	203,195		$	34,605	$	1,237,455		$	(3,286,522	)
Interest expense, net	24,256			10,754		133,235			393,549
Depreciation, depletion and amortization	122,464			32,604		191,581			379,345
Accretion on asset retirement obligations	30,209			7,634		24,321			33,680
Amortization of sales contracts, net	53,985			796		(728		)	(8,811		)
Asset impairment and mine closure costs	—			—		129,267			2,628,303
Losses from disposed operations resulting from Patriot Coal bankruptcy	—			—		—			116,343
Gain on sale of Lone Mountain Processing, Inc.	(21,297		)	—		—			—
Net loss resulting from early retirement of debt and debt restructuring	2,547			—		2,213			27,910
Reorganization items, net	2,398			759		(1,630,041		)	—
Fresh start coal inventory fair value adjustment	—			7,345		—			—
Adjusted EBITDAR	$	417,757		$	94,497	$	87,303		$	283,797

Quarterly Selected Financial Data (unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information



Year Ended December 31, 2017	March 31			June 30			September 30			December 31

(In thousands, except per share data)

Revenues	$	600,975		$	549,866		$	613,538		560,244
Gross profit	$	85,747		$	62,577		$	65,100		62,937
Income from operations	$	66,264		$	42,692		$	72,489		$	50,951
Reorganization items, net	$	(2,828	)	$	(21	)	$	(43	)	$	494
Net income	$	51,668		$	37,160		$	68,351		$	81,271
Diluted income per common share	$	2.03		$	1.48		$	2.83		$	3.64



	Predecessor											Successor
Year Ended December 31, 2016	March 31			June 30			September 30			October 1		October 2 through December 31, 2016
	(a) (b)			(a) (b)			(b)			(b)
(In thousands, except per share data)

Revenues	$	428,106		$	420,298		$	550,305		$	—	$	575,688
Gross profit (loss)	$	(53,325	)	$	(56,469	)	$	31,042		$	—	$	64,458
Asset impairment and mine closure costs	$	85,520		$	43,701		$	46		$	—	$	—
Income (loss) from operations	$	(158,412	)	$	(110,521	)	$	11,795		$	—	$	46,118
Reorganization items, net	$	(3,875	)	$	(21,271	)	$	(20,904	)	$	1,676,091	$	(759	)
Net income (loss)	$	(206,702	)	$	(175,887	)	$	(51,421	)	$	1,676,091	$	33,449
Diluted income (loss) per common share	$	(9.71	)	$	(8.26	)	$	(2.41	)	$	78.66	$	1.31

(b) The Company filed for bankruptcy on January 11, 2016 and subsequently emerged on October 5, 2016. See further discussion in Note 3, “Emergence from Bankruptcy and Fresh Start Accounting.”

Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Statutory Accounting Practices
Mineral rights	$ 361.2	$ 381.0
Deferred finance costs, net	5.3	5.2
Deferred finance costs, current	$ 2.3	$ 1.9
Exploration and production equipment \| Minimum
Statutory Accounting Practices
Estimated useful life	7 years
Exploration and production equipment \| Maximum
Statutory Accounting Practices
Estimated useful life	18 years
Building and building improvements \| Minimum
Statutory Accounting Practices
Estimated useful life	1 year
Building and building improvements \| Maximum
Statutory Accounting Practices
Estimated useful life	21 years
Mining properties and mineral rights \| Minimum
Statutory Accounting Practices
Term of contract	10 years
Mining properties and mineral rights \| Maximum
Statutory Accounting Practices
Term of contract	50 years

(Treatment of Claims and New First Lien Debt Facility) (Details)	Oct. 05, 2016 USD ($) $ / shares
Fresh-Start Adjustment [Line Items]
Holders of allowed claims pro-rata amount of cash to settle claims	$ 144,800,000.0
Holders of allowed claims amount of cash to settle claims	$ 30,000,000
Holders of allowed claims percentage of common stock outstanding upon reorganization	94.00%
Holders of allowed claims warrant exercise period	7 years
Holders of allowed claims total equity value of common stock	$ 1,425,000,000
Exercise price of warrants (in usd per share) \| $ / shares	$ 57
Holders of allowed claims percentage of common stock outstanding pursuant to incentive plan upon reorganization	10.00%
Unsecured note holders pro rata amount of cash to settle claims	$ 22,636,000
Unsecured note holders pro rata amount of cash in lieu of warrants	$ 25,000,000
Unsecured note holders percentage of common stock outstanding upon reorganization	6.00%
Other general holders pro rata amount of cash to settle claims	$ 7,364,000
Other general holders professional expenses retained by claims committee	200,000
New first lien debt facility \| Senior notes
Fresh-Start Adjustment [Line Items]
Amount of debt instrument	$ 326,500,000.0
Class A Common Stock
Fresh-Start Adjustment [Line Items]
Holders of allowed claims percentage of common stock outstanding upon reorganization	12.00%

(Securitization Facility and Warrant Agreement) (Details) - USD ($)	Oct. 05, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 02, 2016
Fresh-Start Adjustment [Line Items]
Common stock, par value (in usd per share)		$ 0.01	$ 0.01
Number of securities called by each warrant (in shares)	1
Exercise price of warrants (in usd per share)	$ 57
Percentage of listed common stock	90.00%
Number of shares of common stock underlying warrant multiplier	$ 0
Class A Common Stock
Fresh-Start Adjustment [Line Items]
Aggregate number of securities called by warrants (in shares)	1,914,856			1,914,856
Common stock, par value (in usd per share)	$ 0.01

(Termination of Material Definitive Agreements, Sale of Equity Securities and Reorganization Value) (Details) - USD ($)	Oct. 05, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 02, 2016	Oct. 01, 2016	Jan. 11, 2016
Fresh-Start Adjustment [Line Items]
Common stock, shares issued (in shares)		25,047,000	25,002,000
Common stock, par value (in usd per share)		$ 0.01	$ 0.01
Reorganization value				$ 687,500,000
Excess cash				64,000,000
Minimum cash balance assumption				$ 250,000,000
Minimum
Fresh-Start Adjustment [Line Items]
Reorganization value					$ 650,000,000
Maximum
Fresh-Start Adjustment [Line Items]
Reorganization value					$ 950,000,000
Discounted cash flow valuation technique \| Minimum
Fresh-Start Adjustment [Line Items]
Discount rate (percent)	13.25%
Discounted cash flow valuation technique \| Maximum
Fresh-Start Adjustment [Line Items]
Discount rate (percent)	15.25%
7.00% senior notes due 2019 at par
Fresh-Start Adjustment [Line Items]
Senior notes interest rate (percent)						7.00%
7.25% senior notes due 2020 at par
Fresh-Start Adjustment [Line Items]
Senior notes interest rate (percent)						7.25%
7.25% senior notes due 2021 at par
Fresh-Start Adjustment [Line Items]
Senior notes interest rate (percent)						7.25%
9.875% senior notes ($375.0 million face value) due 2019
Fresh-Start Adjustment [Line Items]
Senior notes interest rate (percent)						9.875%
8.00% senior secured notes due 2019 at par
Fresh-Start Adjustment [Line Items]
Senior notes interest rate (percent)						8.00%
Class A Common Stock
Fresh-Start Adjustment [Line Items]
Common stock, shares issued (in shares)				24,589,834
Common stock, par value (in usd per share)	$ 0.01
Aggregate number of securities called by warrants (in shares)	1,914,856			1,914,856
Class B Common Stock
Fresh-Start Adjustment [Line Items]
Common stock, shares issued (in shares)				410,166
Common stock, par value (in usd per share)				$ 0.01
New first lien debt facility \| Senior notes
Fresh-Start Adjustment [Line Items]
Amount of debt instrument	$ 326,500,000.0

Emergence from Bankruptcy and Fresh Start Accounting (Accounting Impact of Emergence) (Details) $ in Thousands	Oct. 01, 2016 USD ($)
Reorganizations [Abstract]
Percentage of voting shares received upon emergence of new entity (percent)	50.00%
Assets
Fresh-Start Adjustment, Increase (Decrease), Property and Equipment, Net	$ (2,363,829)
Fresh Start Adjustments
Assets
Fresh-Start Adjustment, Increase (Decrease), Receivables, Net	779
Fresh-Start Adjustment, Increase (Decrease), Inventories	(21,078)
Fresh-Start Adjustment, Increase (Decrease), Prepaid and Other Current Assets	53,851
Fresh-Start Adjustment, Increase (Decrease), Current Assets	33,552
Fresh-Start Adjustment, Increase (Decrease), Property and Equipment, Net	(2,363,829)
Fresh-Start Adjustment, Increase (Decrease), Prepaid Royalties	(20,997)
Fresh-Start Adjustment, Increase (Decrease), Equity Investments	(61,606)
Fresh-Start Adjustment, Increase (Decrease), Other Assets, Noncurrent	37,503
Fresh-Start Adjustment, Increase (Decrease), Other Assets	(45,100)
Fresh-Start Adjustment, Increase (Decrease), Assets	(2,375,377)
Liabilities not subject to compromise
Fresh-Start Adjustment, Increase (Decrease), Accounts Payable	(250)
Fresh-Start Adjustment, Increase (Decrease), Accrued Liabilities and Other Current Liabilities	26,644
Fresh-Start Adjustment, Increase (Decrease), Current Liabilities	26,394
Fresh-Start Adjustment, Increase (Decrease), Asset Retirement Obligations	(60,570)
Fresh-Start Adjustment, Increase (Decrease), Pension Obligations	24,565
Fresh-Start Adjustment, Increase (Decrease), Other Postretirement Obligations	24,836
Fresh-Start Adjustment, Increase (Decrease), Accrued Workers' Compensation	74,520
Fresh-Start Adjustment, Increase (Decrease), Noncurrent Other Obligations	888
Fresh-Start Adjustment, Increase (Decrease), Other Noncurrent Obligations	90,633
Fresh-Start Adjustment, Increase (Decrease), Liabilities	90,633
Stockholders’ equity (deficit)
Fresh-Start Adjustment, Increase (Decrease), Retained Earnings (Deficit)	(2,467,716)
Fresh-Start Adjustment, Increase (Decrease), Accumulated Other Comprehensive Income (Loss)	1,706
Fresh-Start Adjustment, Increase (Decrease), Stockholders' Equity	(2,466,010)
Fresh-Start Adjustment, Increase (Decrease), Liabilities and Stockholders' Equity	(2,375,377)
Effect of Plan
Assets
Fresh-Start Adjustment, Increase (Decrease), Cash and Cash Equivalents	(199,718)
Fresh-Start Adjustment, Increase (Decrease), Prepaid and Other Current Assets	6,367
Fresh-Start Adjustment, Increase (Decrease), Current Assets	(193,351)
Fresh-Start Adjustment, Increase (Decrease), Other Assets, Noncurrent	34,495
Fresh-Start Adjustment, Increase (Decrease), Other Assets	34,495
Fresh-Start Adjustment, Increase (Decrease), Assets	(158,856)
Liabilities not subject to compromise
Fresh-Start Adjustment, Increase (Decrease), Accrued Liabilities and Other Current Liabilities	(36,331)
Fresh-Start Adjustment, Increase (Decrease), Current Maturities of Long-term Debt	3,265
Fresh-Start Adjustment, Increase (Decrease), Current Liabilities	(33,066)
Fresh-Start Adjustment, Increase (Decrease), Long-term Debt	323,235
Fresh-Start Adjustment, Increase (Decrease), Other Noncurrent Obligations	290,169
Fresh-Start Adjustment, Increase (Decrease), Liabilities Subject to Compromise	(5,278,612)
Fresh-Start Adjustment, Increase (Decrease), Liabilities	(4,988,443)
Stockholders’ equity (deficit)
Fresh-Start Adjustment, Increase (Decrease), Preferred and Common Stock Held in Treasury	53,863
Fresh-Start Adjustment, Increase (Decrease), Retained Earnings (Deficit)	7,146,693
Fresh-Start Adjustment, Increase (Decrease), Stockholders' Equity	4,829,587
Fresh-Start Adjustment, Increase (Decrease), Liabilities and Stockholders' Equity	(158,856)
Predecessor
Preconfirmation
Preconfirmation, Cash and cash equivalents	400,205
Preconfirmation, Short term investments	111,451
Preconfirmation, Restricted cash	81,563
Preconfirmation, Trade accounts receivable	165,522
Preconfirmation, Other Receivables	17,227
Preconfirmation, Inventories	159,410
Preconfirmation, Prepaid Royalties, Current	4,805
Preconfirmation, Deferred Income Tax Assets, Current	0
Preconfirmation, Coal Derivative Assets	2,180
Preconfirmation, Prepaid and Other Current Assets	36,960
Preconfirmation, Current Assets	979,323
Preconfirmation, Property and Equipment, Net	3,434,941
Preconfirmation, Prepaid Royalties, Noncurrent	20,997
Preconfirmation, Investments	164,232
Preconfirmation, Other Assets, Noncurrent	58,569
Preconfirmation, Other Assets	243,798
Preconfirmation, Assets	4,658,062
Preconfirmation, Accounts Payable	74,595
Precomfirmation, Accrued expenses and other current liabilities	225,739
Preconfirmation, Current Maturities of Long-term Debt	3,397
Preconfirmation, Current Liabilities	303,731
Preconfirmation, Long-term Debt	30,037
Preconfirmation, Asset Retirement Obligations	394,699
Preconfirmation, Pension Obligations	23,716
Preconfirmation, Other Postretirement Obligations	87,123
Preconfirmation, Accrued Workers' Compensation	119,828
Preconfirmation, Deferred Income Tax Liabilities	0
Preconfirmation, Noncurrent Other Obligations	96,410
Preconfirmation, Liabilities Not Subject to Compromise	1,055,544
Preconfirmation, Liabilities Subject to Compromise	5,278,612
Preconfirmation, Liabilities	6,334,156
Preconfirmation, Common Stock	2,145
Preconfirmation, Additional Paid-in Capital	3,056,307
Preconfirmation, Preferred and Common Stock Held in Treasury	(53,863)
Preconfirmation, Retained Earnings (Deficit)	(4,678,977)
Preconfirmation, Accumulated Other Comprehensive Income (Loss)	(1,706)
Preconfirmation, Stockholders' Equity	(1,676,094)
Preconfirmation, Liabilities and Stockholders' Equity	4,658,062
Stockholders’ equity (deficit)
Fresh-Start Adjustment, Increase (Decrease), Common Stock	(2,145)
Fresh-Start Adjustment, Increase (Decrease), Additional Paid-in Capital	(3,056,307)
Fresh-Start Adjustment, Increase (Decrease), Preferred and Common Stock Held in Treasury	53,863
Fresh-Start Adjustment, Increase (Decrease), Retained Earnings (Deficit)	7,146,693
Predecessor \| Effect of Plan
Stockholders’ equity (deficit)
Fresh-Start Adjustment, Increase (Decrease), Common Stock	(2,145)
Fresh-Start Adjustment, Increase (Decrease), Additional Paid-in Capital	(3,056,307)
Successor
Postconfirmation
Postconfirmation, Cash and Cash Equivalents	200,487
Postconfirmation, Short-term Investments	111,451
Postconfirmation, Restricted Cash and Cash Equivalents, Current	81,563
Postconfirmation, Receivables, Net	165,522
Postconfirmation, Other Receivables	18,006
Postconfirmation, Inventories	138,332
Postconfirmation, Prepaid Royalties, Current	4,805
Postconfirmation, Deferred Income Tax Assets, Current	0
Postconfirmation, Coal Derivative Assets	2,180
Postconfirmation, Prepaid and Other Current Assets	97,178
Postconfirmation, Current Assets	819,524
Postconfirmation, Property and Equipment, Net	1,071,112
Postconfirmation, Prepaid Royalties, Noncurrent	0
Postconfirmation, Investments	102,626
Postconfirmation, Other Assets, Noncurrent	130,567
Postconfirmation, Other Assets	233,193
Postconfirmation, Assets	2,123,829
Postconfirmation, Accounts Payable	74,345
Postcomfirmation, Accrued expenses and other current liabilities	216,052
Postconfirmation, Current Maturities of Long-term Debt	6,662
Postconfirmation, Current Liabilities	297,059
Postconfirmation, Long-term Debt	353,272
Postconfirmation, Asset Retirement Obligations	334,129
Postconfirmation, Pension Obligations	48,281
Postconfirmation, Other Postretirement Obligations	111,959
Postconfirmation, Accrued Workers' Compensation	194,348
Postconfirmation, Deferred Income Tax Liabilities	0
Postconfirmation, Noncurrent Other Obligations	97,298
Postconfirmation, Liabilities Not Subject to Compromise	1,436,346
Postconfirmation, Liabilities Subject to Compromise	0
Postconfirmation, Liabilities	1,436,346
Postconfirmation, Common Stock	250
Postconfirmation, Additional Paid-in Capital	687,233
Postconfirmation, Preferred and Common Stock Held in Treasury	0
Postconfirmation, Retained Earnings (Deficit)	0
Postconfirmation, Accumulated Other Comprehensive Income (Loss)	0
Postconfirmation, Stockholders' Equity	687,483
Postconfirmation, Liabilities and Stockholders' Equity	2,123,829
Successor \| Effect of Plan
Stockholders’ equity (deficit)
Fresh-Start Adjustment, Increase (Decrease), Common Stock	250
Fresh-Start Adjustment, Increase (Decrease), Additional Paid-in Capital	$ 687,233

Emergence from Bankruptcy and Fresh Start Accounting (Liabilities Subject to Compromise) (Details) $ in Thousands	Oct. 01, 2016 USD ($)
Reorganizations [Abstract]
Liabilities subject to compromise	$ 5,278,612
Common stock (at par) Successor	(250)
Warrants Successor	(14,822)
Paid-in capital Successor	(672,411)
Issuance of Term Loan Successor	(326,500)
Cash payment to settle claims and professional fees	(122,525)
Total pre-tax gain on plan effects	$ 4,142,104

Emergence from Bankruptcy and Fresh Start Accounting (Cash Used) (Details) $ in Thousands	Oct. 05, 2016 USD ($)
Reorganizations [Abstract]
Payment to secured lenders	$ 43,496
Payments to unsecured creditors	42,399
Final adequate protection payment	36,331
Collateral requirements	31,665
Professional fees	31,630
Other	14,197
Total cash outflow at emergence	$ 199,718

Emergence from Bankruptcy and Fresh Start Accounting (Unsecured or Under-Secured Liabilities Previously Reported) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Oct. 01, 2016	Jan. 11, 2016
Fresh-Start Adjustment [Line Items]
Accrued expenses and other current liabilities	$ 184,161	$ 205,240
Accounts payable	134,137	95,953
Other noncurrent liabilities	$ 59,457	$ 63,824
Liabilities Subject to Compromise			$ 5,278,612
Scenario, previously reported
Fresh-Start Adjustment [Line Items]
Debt				$ 5,026,806
Accrued expenses and other current liabilities				136,295
Accounts payable				106,297
Other noncurrent liabilities				9,214
Liabilities Subject to Compromise				$ 5,278,612

Emergence from Bankruptcy and Fresh Start Accounting (Reorganization Adjustments and Property, Plant and Equipment) (Details) - USD ($) $ in Thousands		3 Months Ended	9 Months Ended	12 Months Ended
	Oct. 01, 2016	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Fresh-Start Adjustment [Line Items]
Total pre-tax gain on plan effects	$ 4,142,104
Property, plant and equipment, net		$ 1,053,603		$ 955,948
Fresh-Start Adjustment, Increase (Decrease), Property and Equipment, Net	(2,363,829)		$ (2,363,829)
Net Coal Properties
Fresh-Start Adjustment [Line Items]
Fresh-Start Adjustment, Increase (Decrease), Property and Equipment, Net	(1,971,314)		(1,971,314)
Net Plant & Equipment
Fresh-Start Adjustment [Line Items]
Fresh-Start Adjustment, Increase (Decrease), Property and Equipment, Net	(405,259)		(405,259)
Net Deferred Charges
Fresh-Start Adjustment [Line Items]
Fresh-Start Adjustment, Increase (Decrease), Property and Equipment, Net	12,744		12,744
Predecessor
Fresh-Start Adjustment [Line Items]
Total pre-tax gain on plan effects	4,142,104		4,142,104		$ 0
Cancellation of predecessor common stock	2,145		2,145
Cancellation of predecessor paid-in capital	3,056,307		3,056,307
Cancellation of predecessor treasury stock	(53,863)		(53,863)
Net impact on accumulated earnings (deficit)	7,146,693		7,146,693
Property, plant and equipment, net	3,434,941		3,434,941
Predecessor \| Net Coal Properties
Fresh-Start Adjustment [Line Items]
Property, plant and equipment, net	2,358,779		2,358,779
Predecessor \| Net Plant & Equipment
Fresh-Start Adjustment [Line Items]
Property, plant and equipment, net	812,888		812,888
Predecessor \| Net Deferred Charges
Fresh-Start Adjustment [Line Items]
Property, plant and equipment, net	263,274		263,274
Successor
Fresh-Start Adjustment [Line Items]
Total pre-tax gain on plan effects		$ 0		$ 0
Property, plant and equipment, net	1,071,112		1,071,112
Successor \| Net Coal Properties
Fresh-Start Adjustment [Line Items]
Property, plant and equipment, net	387,465		387,465
Successor \| Net Plant & Equipment
Fresh-Start Adjustment [Line Items]
Property, plant and equipment, net	407,629		407,629
Successor \| Net Deferred Charges
Fresh-Start Adjustment [Line Items]
Property, plant and equipment, net	$ 276,018		$ 276,018

Emergence from Bankruptcy and Fresh Start Accounting (Additional Information to Liabilities Subject to Compromise) (Details) - USD ($) $ in Thousands	Oct. 05, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2016
Fresh-Start Adjustment [Line Items]
Fair value of senior notes and other long-term debt, including amounts classified as current			$ 336,100	$ 362,900
Current maturities of debt			15,783	11,038
Insurance receivable, current			3,300	$ 800
Decrease in property plant and equipment, net		$ 2,363,829
Successor
Fresh-Start Adjustment [Line Items]
Current maturities of debt			$ 15,783
Term loan due 2021 \| Successor
Fresh-Start Adjustment [Line Items]
Fair value of senior notes and other long-term debt, including amounts classified as current		326,500
Current maturities of debt		$ 3,300
Minimum \| Discounted cash flow valuation technique
Fresh-Start Adjustment [Line Items]
Discount rate (percent)	13.25%
Maximum \| Discounted cash flow valuation technique
Fresh-Start Adjustment [Line Items]
Discount rate (percent)	15.25%
Asset Retirement Obligation Costs \| Minimum \| Discounted cash flow valuation technique
Fresh-Start Adjustment [Line Items]
Discount rate (percent)		7.06%
Asset Retirement Obligation Costs \| Maximum \| Discounted cash flow valuation technique
Fresh-Start Adjustment [Line Items]
Discount rate (percent)		9.08%
Net Plant & Equipment
Fresh-Start Adjustment [Line Items]
Decrease in property plant and equipment, net		$ 405,259
Net Plant & Equipment \| Market Approach and Cost Approach Valuation Techniques \| Successor
Fresh-Start Adjustment [Line Items]
Fair value of property, plant and equipment, net		407,600
Net Coal Properties
Fresh-Start Adjustment [Line Items]
Decrease in property plant and equipment, net		1,971,314
Net Coal Properties \| Discounted Cash Flow and Market Approach Valuation Techniques \| Successor
Fresh-Start Adjustment [Line Items]
Fair value of property, plant and equipment, net		387,500
Fresh Start Adjustments
Fresh-Start Adjustment [Line Items]
Increase (decrease) in inventories		(21,078)
Increase in current above market sales contracts		71,100
Decrease in prepaid expenses		11,300
Decrease in property plant and equipment, net		2,363,829
Increase in noncurrent above market sales contract		26,000
Increase in noncurrent insurance receivables		18,600
Decrease in noncurrent prepaid balances		13,200
Increase in current below market sales contracts		27,800
Increase in noncurrent below market sales contracts		3,900
Decrease in miscellaneous noncurrent liabilities		3,100
Fresh Start Adjustments \| Coal Inventory
Fresh-Start Adjustment [Line Items]
Increase (decrease) in inventories		7,300
Fresh Start Adjustments \| Critical Spare Parts
Fresh-Start Adjustment [Line Items]
Increase (decrease) in inventories		$ (28,400)
Equity Method Investments \| Level 3 \| Discounted Cash Flow Approach and Comparable Company Approach
Fresh-Start Adjustment [Line Items]
Discount rate (percent)		14.00%

Emergence from Bankruptcy and Fresh Start Accounting (Reorganization Items, Net and Contractual Interest Expense During Bankruptcy) (Details) - USD ($) $ in Thousands		3 Months Ended								9 Months Ended	12 Months Ended
	Oct. 01, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Fresh-Start Adjustment [Line Items]
Gain on settlement of claims	$ 4,142,104
Successor
Fresh-Start Adjustment [Line Items]
Gain on settlement of claims						$ 0					$ 0
Fresh start adjustments						0					0
Professional fees						(759)					(2,398)
Reorganization Items		$ 494				(759)					$ (2,398)
Predecessor
Fresh-Start Adjustment [Line Items]
Gain on settlement of claims	4,142,104									$ 4,142,104		$ 0
Fresh start adjustments										(2,466,010)		0
Professional fees										(46,053)		0
Reorganization Items	$ 1,676,091		$ (43)	$ (21)	$ (2,828)	(759)	$ (20,904)	$ (21,271)	$ (3,875)	$ 1,630,041		$ 0
Contractual interest expense						300,900
Interest Expense						$ 135,900

Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Fresh start accounting adjustment		$ 1,706
Predecessor
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Unrealized gains (losses)		563
Amounts reclassified from accumulated other comprehensive income (loss)		(454)
Predecessor \| Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	$ 0	(1,815)
Ending balance		0
Predecessor \| Derivative Instruments
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	0	325
Unrealized gains (losses)		(138)
Amounts reclassified from accumulated other comprehensive income (loss)		(316)
Fresh start accounting adjustment		129
Ending balance		0
Predecessor \| Pension, Postretirement and Other Post-Employment Benefits
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	0	(721)
Amounts reclassified from accumulated other comprehensive income (loss)		(1,363)
Fresh start accounting adjustment		2,084
Ending balance		0
Predecessor \| Available-for-Sale Securities
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	0	(1,419)
Unrealized gains (losses)		701
Amounts reclassified from accumulated other comprehensive income (loss)		1,225
Fresh start accounting adjustment		(507)
Ending balance		$ 0
Successor
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Unrealized gains (losses)	24,454		$ (3,092)
Amounts reclassified from accumulated other comprehensive income (loss)	0		(995)
Successor \| Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance			24,454
Ending balance	24,454		20,367
Successor \| Derivative Instruments
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance			0
Unrealized gains (losses)	0		497
Amounts reclassified from accumulated other comprehensive income (loss)	0		150
Ending balance	0		647
Successor \| Pension, Postretirement and Other Post-Employment Benefits
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance			24,067
Unrealized gains (losses)	24,067		(3,589)
Amounts reclassified from accumulated other comprehensive income (loss)	0		(758)
Ending balance	24,067		19,720
Successor \| Available-for-Sale Securities
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance			387
Unrealized gains (losses)	387		0
Amounts reclassified from accumulated other comprehensive income (loss)	0		(387)
Ending balance	$ 387		$ 0

Accumulated Other Comprehensive Income (Loss) (Schedule of Reclassifications) (Details) - USD ($) $ in Thousands		3 Months Ended								9 Months Ended	12 Months Ended
	Oct. 01, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Revenues						$ 575,688					$ 2,324,623
Interest expense						(10,754)					(24,256)
Provision for (benefit from) income taxes						(1,156)					35,255
Income (loss) before income taxes						34,605					203,195
Net income (loss)						33,449					238,450
Successor
Accumulated Other Comprehensive Income (Loss) [Line Items]
Revenues		$ 560,244				575,688					2,324,623
Revenues, coal hedges						174,097					793,594
Interest expense						(10,754)					(24,256)
Provision for (benefit from) income taxes						(1,156)					35,255
Income (loss) before income taxes						34,605					203,195
Net income (loss)		$ 81,271				33,449
Successor \| Pension, Postretirement and Other Post-Employment Benefits
Accumulated Other Comprehensive Income (Loss) [Line Items]
Provision for (benefit from) income taxes						0					0
Amortization of prior service credits						0					0
Amortization of net actuarial gains (losses)						0					0
Curtailments						0					(773)
Settlements						0					1,531
Income (loss) before income taxes						0					758
Net income (loss)						0					758
Successor \| Reclassification out of accumulated other comprehensive income \| Derivative Instruments \| Commodity Contract
Accumulated Other Comprehensive Income (Loss) [Line Items]
Revenues
Revenues, coal hedges						0					0
Interest expense											(150)
Provision for (benefit from) income taxes						0					0
Net income (loss)						0					(150)
Successor \| Reclassification out of accumulated other comprehensive income \| Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Provision for (benefit from) income taxes						0					0
Interest and investment income						0					387
Net income (loss)						$ 0					$ 387
Predecessor
Accumulated Other Comprehensive Income (Loss) [Line Items]
Revenues			$ 613,538	$ 549,866	$ 600,975		$ 550,305	$ 420,298	$ 428,106	$ 1,398,709		$ 2,573,260
Revenues, coal hedges										280,879		395,323
Interest expense										(133,235)		(393,549)
Provision for (benefit from) income taxes										4,626		373,380
Income (loss) before income taxes										1,237,455		(3,286,522)
Net income (loss)	$ 1,676,091		$ 68,351	$ 37,160	$ 51,668		$ (51,421)	$ (175,887)	$ (206,702)	1,242,081		$ (2,913,142)
Predecessor \| Pension, Postretirement and Other Post-Employment Benefits
Accumulated Other Comprehensive Income (Loss) [Line Items]
Provision for (benefit from) income taxes										(481)
Amortization of prior service credits										7,854
Amortization of net actuarial gains (losses)										(6,010)
Curtailments										0
Settlements										0
Income (loss) before income taxes										1,844
Net income (loss)										1,363
Predecessor \| Reclassification out of accumulated other comprehensive income \| Derivative Instruments \| Commodity Contract
Accumulated Other Comprehensive Income (Loss) [Line Items]
Revenues
Revenues, coal hedges										397
Interest expense										0
Provision for (benefit from) income taxes										(81)
Net income (loss)										316
Predecessor \| Reclassification out of accumulated other comprehensive income \| Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Provision for (benefit from) income taxes										1,038
Interest and investment income										(2,263)
Net income (loss)										$ (1,225)

Divestitures (Narrative) (Details) $ in Thousands		3 Months Ended	12 Months Ended
Divestitures (Narrative) (Details) $ in Thousands	Sep. 14, 2017 USD ($) company	Dec. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of Lone Mountain Processing, Inc.		$ 0	$ 21,297
Lone Mountain Processing LLC \| Discontinued operations, disposed of by sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of mining companies \| company	2
Proceeds from sale	$ 8,300
Disbursements related to landholder consent fees and professional fees	(1,400)
Gain on sale of Lone Mountain Processing, Inc.	21,300
Pension Benefits \| Lone Mountain Processing LLC \| Discontinued operations, disposed of by sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Curtailment gains	$ 4,700

Impairment Charges and Mine Closure Costs (Summary Asset Impairments and Mine Closure Costs) (Details) - USD ($) $ in Thousands	3 Months Ended							6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2015	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment and mine closure costs	$ 0				$ 500,000	$ 2,100,000	$ 19,100	$ 2,600,000		$ 0
Successor
Impaired Long-Lived Assets Held and Used [Line Items]
Coal lands and mineral rights	0									0
Plant and equipment	0									0
Deferred development	0									0
Prepaid royalties	0									0
Equity investments	0									0
Inventories	0									0
Other	0									0
Asset impairment and mine closure costs	$ 0									$ 0
Predecessor
Impaired Long-Lived Assets Held and Used [Line Items]
Coal lands and mineral rights									$ 74,144		$ 2,210,488
Plant and equipment									0		199,107
Deferred development									0		159,474
Prepaid royalties									3,406		41,990
Equity investments									40,920		21,325
Inventories									0		66
Other									10,797
Other											(4,147)
Asset impairment and mine closure costs		$ 46	$ 43,701	$ 85,520					$ 129,267		$ 2,628,303

Impairment Charges and Mine Closure Costs (Details) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended	12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Jun. 30, 2016	Dec. 31, 2015	Oct. 01, 2016	Dec. 31, 2017
Impaired Long-Lived Assets Held and Used [Line Items]
Other-than-temporary impairment loss on available-for-sale securities			$ 2,900
Severance costs							$ 7,200
Curtailments							$ 3,600
Asset impairment and mine closure costs	$ 0			$ 500,000	$ 2,100,000	$ 19,100		$ 2,600,000		$ 0
Impairment charge of higher-cost mining complex						5,600
Royalty Agreements
Impaired Long-Lived Assets Held and Used [Line Items]
Prepaid royalties			3,400			$ 12,200
MET
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment and mine closure costs									$ 2,200,000
Other Thermal
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment and mine closure costs									$ 400,000
Kentucky
Impaired Long-Lived Assets Held and Used [Line Items]
Net book value of idled facility			$ 74,100
Longview, Washington
Impaired Long-Lived Assets Held and Used [Line Items]
Other-than-temporary impairment loss on available-for-sale securities		$ 38,000

Losses from disposed operations resulting from Patriot Coal Bankruptcy (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Nov. 22, 2016	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Losses related to previously disposed off operations		$ 0	$ (21,297)
Discontinued Operations, Held-for-sale or Disposed of by Sale \| Magnum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Losses related to previously disposed off operations				$ 116,300
Surety Bond \| Magnum
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Decease in collateral held by bonding company	$ 20,000

Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Inventories	$ 128,960	$ 113,462
Allowance for slow-moving and obsolete inventories	300	0
Successor
Property, Plant and Equipment [Line Items]
Coal	54,692
Repair parts and supplies	74,268
Inventories	$ 128,960
Predecessor
Property, Plant and Equipment [Line Items]
Coal		37,268
Repair parts and supplies		76,194
Inventories		$ 113,462

Investments in Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Debt securities, current	$ 155,846	$ 88,072
Total investments, cost basis	156,189	89,910
Total investments, accumulated gross unrealized gains	22	388
Total investments, accumulated gross unrealized losses	(365)	(89)
Total investments, fair value	155,846	90,209
Short-term investments
Schedule of Available-for-sale Securities [Line Items]
Total investments, current	155,846	88,072
Other assets
Schedule of Available-for-sale Securities [Line Items]
Total investments, noncurrent	0	2,137
U.S. government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Debt securities, cost basis	64,151
Debt securities, accumulated gross unrealized gains	22
Debt securities, accumulated gross unrealized losses	(73)
Debt securities, fair value	64,100
U.S. government and agency securities \| Short-term investments
Schedule of Available-for-sale Securities [Line Items]
Debt securities, current	64,100
U.S. government and agency securities \| Other assets
Schedule of Available-for-sale Securities [Line Items]
Debt securities, noncurrent		0
Corporate notes and bonds
Schedule of Available-for-sale Securities [Line Items]
Debt securities, cost basis	92,038	88,161
Debt securities, accumulated gross unrealized gains	0	0
Debt securities, accumulated gross unrealized losses	(292)	(89)
Debt securities, fair value	91,746	88,072
Corporate notes and bonds \| Short-term investments
Schedule of Available-for-sale Securities [Line Items]
Debt securities, current	$ 91,746	88,072
Corporate notes and bonds \| Other assets
Schedule of Available-for-sale Securities [Line Items]
Debt securities, noncurrent		0
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Debt securities, cost basis		1,749
Debt securities, accumulated gross unrealized gains		388
Debt securities, accumulated gross unrealized losses		0
Debt securities, fair value		2,137
Equity securities \| Short-term investments
Schedule of Available-for-sale Securities [Line Items]
Debt securities, current		0
Equity securities \| Other assets
Schedule of Available-for-sale Securities [Line Items]
Debt securities, noncurrent		$ 2,137

Investments in Available-for-Sale Securities (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities [Abstract]
Continuous unrealized loss position for less than a year	$ 132.0	$ 47.6
Continuous unrealized loss position for over a year	$ 0.0	$ 40.4

Equity Method Investments and Membership Interests in Joint Ventures (Schedule of Equity Method Investments) (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended	12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Sep. 30, 2015	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance					$ 96,074
Ending Balance	$ 96,074				106,107
Millennium
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Impairment of equity investment		$ (38,000)
Tongue River
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Impairment of equity investment			$ (21,300)
Predecessor
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance	102,625			$ 201,877		$ 235,842
Advances to (distributions from) affiliates, net				(4,934)		(18,360)
Equity in comprehensive income (loss)				5,314		7,979
Impairment of equity investment				(38,025)		(21,325)
Sale of equity investment						(2,259)
Fresh start accounting adjustment				(61,607)
Ending Balance				102,625		201,877
Predecessor \| Knight Hawk
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance	94,000			151,592		158,477
Advances to (distributions from) affiliates, net				(8,374)		(29,862)
Equity in comprehensive income (loss)				9,033		22,977
Fresh start accounting adjustment				(58,251)
Ending Balance				94,000		151,592
Predecessor \| DTA
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance	8,600			13,239		13,738
Advances to (distributions from) affiliates, net				1,474		3,207
Equity in comprehensive income (loss)				(2,095)		(3,706)
Fresh start accounting adjustment				(4,018)
Ending Balance				8,600		13,239
Predecessor \| Millennium
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance				37,589		40,223
Advances to (distributions from) affiliates, net				1,966		7,052
Equity in comprehensive income (loss)				(1,530)		(9,686)
Impairment of equity investment				(38,025)
Fresh start accounting adjustment				0
Ending Balance						37,589
Predecessor \| Tongue River
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance						20,740
Advances to (distributions from) affiliates, net						913
Equity in comprehensive income (loss)						(328)
Impairment of equity investment						(21,325)
Fresh start accounting adjustment				0
Predecessor \| Other
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance	25			(543)		2,664
Advances to (distributions from) affiliates, net						330
Equity in comprehensive income (loss)				(94)		(1,278)
Sale of equity investment						(2,259)
Fresh start accounting adjustment				662
Ending Balance				$ 25		$ (543)
Successor
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance					96,074
Advances to (distributions from) affiliates, net	(8,254)				(5,722)
Equity in comprehensive income (loss)	1,703				8,597
Investments in affiliates					7,158
Ending Balance	96,074				106,107
Successor \| Knight Hawk
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance					87,493
Advances to (distributions from) affiliates, net	(9,076)				(8,736)
Equity in comprehensive income (loss)	2,569				11,409
Ending Balance	87,493				90,166
Successor \| DTA
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance					8,581
Advances to (distributions from) affiliates, net	822				3,014
Equity in comprehensive income (loss)	(841)				(2,812)
Investments in affiliates					7,158
Ending Balance	8,581				15,941
Successor \| Millennium
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance					0
Advances to (distributions from) affiliates, net	0				0
Equity in comprehensive income (loss)	0				0
Ending Balance	0				0
Successor \| Tongue River
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance					0
Advances to (distributions from) affiliates, net	0				0
Equity in comprehensive income (loss)	0				0
Ending Balance	0				0
Successor \| Other
Investments in and Advances to Affiliates, at Fair Value [Roll Forward]
Beginning Balance					0
Advances to (distributions from) affiliates, net	0				0
Equity in comprehensive income (loss)	(25)				0
Ending Balance	$ 0				$ 0

Equity Method Investments and Membership Interests in Joint Ventures (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Mar. 31, 2017	Jun. 30, 2016	Sep. 30, 2015	Dec. 31, 2017	Mar. 01, 2017	Dec. 31, 2016
Knight Hawk
Schedule of Equity Method Investments [Line Items]
Ownership interest (percent)				49.00%
DTA
Schedule of Equity Method Investments [Line Items]
Ownership interest (percent)	35.00%				21.875%
Payments to auction house to increase ownership	$ 7.2
Millennium
Schedule of Equity Method Investments [Line Items]
Ownership interest (percent)						38.00%
Impairment of equity investment		$ 38.0
Tongue River
Schedule of Equity Method Investments [Line Items]
Ownership interest (percent)						35.00%
Impairment of equity investment			$ 21.3

Sales Contracts (Schedule of Sales Contracts) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets And Liabilities By Major Class [Line Items]
Acquired fair value, Assets	$ 97,196	$ 97,196
Acquired fair value, Liabilities	31,742	31,742
Accumulated amortization, Asset	(84,760)	(25,625)
Accumulated amortization, Liabilities	(29,979)	(24,829)
Total, Assets	12,436	71,571
Total, Liabilities	1,763	6,913
Net total, Liabilities	10,673	64,658
Coal Supply Agreement, Liabilities	934	5,114
Other current assets
Acquired Finite-Lived Intangible Assets And Liabilities By Major Class [Line Items]
Coal supply agreement, Assets	12,432	59,702
Other current liabilities
Acquired Finite-Lived Intangible Assets And Liabilities By Major Class [Line Items]
Coal Supply Agreement, Liabilities	934	5,114
Other noncurrent assets
Acquired Finite-Lived Intangible Assets And Liabilities By Major Class [Line Items]
Coal supply agreement, Assets	4	11,869
Other noncurrent liabilities
Acquired Finite-Lived Intangible Assets And Liabilities By Major Class [Line Items]
Coal Supply Agreement, Liabilities	$ 829	$ 1,799

Derivatives (Narrative) (Details) $ in Thousands, gal in Millions	9 Months Ended	12 Months Ended
	Oct. 01, 2016 USD ($)	Dec. 31, 2017 USD ($) $ / option gal	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($)
Derivative [Line Items]
Right to reclaim cash collateral, asset		$ 50,042		$ 69,247
Right to reclaim cash collateral, liability		50,042		69,247
Net unrealized and realized gains (losses) related to trading portfolio	$ (900)	(2,000)	$ 5,700
Derivative contracts expected to be reclassified from OCI into earnings		(1,200)
2018
Derivative [Line Items]
Value of trading portfolio realized		$ (1,200)
Diesel purchases \| Heating oil
Derivative [Line Items]
Quantities under derivative contracts \| gal		26.2
Average strike price (in dollars per option) \| $ / option		1.84
Diesel purchases \| Minimum
Derivative [Line Items]
Gallons of diesel fuel purchased annually \| gal		42.0
Diesel purchases \| Maximum
Derivative [Line Items]
Gallons of diesel fuel purchased annually \| gal		46.0
Other current liabilities
Derivative [Line Items]
Right to reclaim cash collateral, liability				$ 2,800
Other current assets
Derivative [Line Items]
Right to reclaim cash collateral, asset		$ 16,200

Derivatives (Schedule of Price Risk Derivatives) (Details) T in Thousands	12 Months Ended
	Dec. 31, 2017 T
Coal sales
Derivative [Line Items]
Derivatives Held	1,865
Coal purchases
Derivative [Line Items]
Derivatives Held	747
2018 \| Coal sales
Derivative [Line Items]
Derivatives Held	1,706
2018 \| Coal purchases
Derivative [Line Items]
Derivatives Held	747
2019 \| Coal sales
Derivative [Line Items]
Derivatives Held	159
2019 \| Coal purchases
Derivative [Line Items]
Derivatives Held	0

Derivatives (Disclosure of Fair Value of Derivatives) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Derivative Assets	$ 55,550	$ 74,155
Derivative Liabilities	(57,259)	(69,348)
Effect of counterparty netting in derivative assets	(50,042)	(69,247)
Effect of counterparty netting in derivative liabilities	50,042	69,247
Net derivative assets as classified in the balance sheet	5,508	4,908
Net derivative liabilities as classified in the balance sheet	(7,217)	(101)
Net derivatives as classified in the balance sheet	(1,709)	4,807
Derivatives Designated as Hedging Instruments \| Coal
Derivative [Line Items]
Derivative Assets	942	0
Derivative Liabilities	(2,146)	(15)
Derivatives Not Designated as Hedging Instruments
Derivative [Line Items]
Derivative Assets	54,608	74,155
Derivative Liabilities	(55,113)	(69,333)
Derivatives Not Designated as Hedging Instruments \| Heating oil -- diesel purchases
Derivative [Line Items]
Derivative Assets	5,354	4,646
Derivatives Not Designated as Hedging Instruments \| Coal held for trading purposes, exchange traded swaps and futures
Derivative [Line Items]
Derivative Assets	44,088	68,948
Derivative Liabilities	(45,221)	(68,740)
Derivatives Not Designated as Hedging Instruments \| Coal
Derivative [Line Items]
Derivative Assets	5,139	475
Derivative Liabilities	(9,892)	(580)
Derivatives Not Designated as Hedging Instruments \| Natural gas
Derivative [Line Items]
Derivative Assets	27	86
Derivative Liabilities	0	(13)
Successor
Derivative [Line Items]
Net derivative assets as classified in the balance sheet	7,339
Net derivative liabilities as classified in the balance sheet	$ (7,217)
Predecessor
Derivative [Line Items]
Net derivative assets as classified in the balance sheet		4,908
Net derivative liabilities as classified in the balance sheet		$ (101)

Derivatives (Net Derivatives as Reflected on the Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ (1,709)	$ 4,807
Other current assets \| Heating oil
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	5,354	4,646
Other current assets \| Coal
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	154	262
Accrued expenses and other current liabilities \| Coal
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ (7,217)	$ (101)

Derivatives (Effects of Derivatives on Measures of Financial Performance) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Successor \| Coal
Derivative Instruments, Gain (Loss) [Line Items]
Coal — unrealized	$ (408)		$ (4,648)
Coal — realized	116		0
Successor \| Heating oil -- diesel purchases
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)	827		(1,057)
Successor \| Natural gas
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)	(91)		(774)
Successor \| Foreign currency
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)	(9)		0
Successor \| Coal contract \| Derivatives Designated as Hedging Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income (Effective Portion)	0		(1,185)
Gains (Losses) Reclassified from Other Comprehensive Income into Income (Effective Portion)	0		0
Predecessor \| Coal
Derivative Instruments, Gain (Loss) [Line Items]
Coal — unrealized		$ (1,662)		$ (3,883)
Coal — realized		(476)		3,236
Predecessor \| Heating oil -- diesel purchases
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)		826		(8,294)
Predecessor \| Natural gas
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)		(463)		878
Predecessor \| Foreign currency
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gains (Losses)		(451)		(867)
Predecessor \| Coal contract \| Derivatives Designated as Hedging Instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income (Effective Portion)		(136)		6,098
Gains (Losses) Reclassified from Other Comprehensive Income into Income (Effective Portion)		397		9,575
Short \| Successor \| Coal contract \| Derivatives Designated as Hedging Instruments \| Sales Revenue, net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income (Effective Portion)	0		(2,127)
Gains (Losses) Reclassified from Other Comprehensive Income into Income (Effective Portion)	0		0
Short \| Predecessor \| Coal contract \| Derivatives Designated as Hedging Instruments \| Sales Revenue, net
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income (Effective Portion)		(672)		12,816
Gains (Losses) Reclassified from Other Comprehensive Income into Income (Effective Portion)		1,634		18,635
Long \| Successor \| Coal contract \| Derivatives Designated as Hedging Instruments \| Cost of Sales
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income (Effective Portion)	0		942
Gains (Losses) Reclassified from Other Comprehensive Income into Income (Effective Portion)	$ 0		$ 0
Long \| Predecessor \| Coal contract \| Derivatives Designated as Hedging Instruments \| Cost of Sales
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income (Effective Portion)		536		(6,718)
Gains (Losses) Reclassified from Other Comprehensive Income into Income (Effective Portion)		$ (1,237)		$ (9,060)

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued Expenses and Other Current Liabilities [Abstract]
Payroll and employee benefits	$ 53,149	$ 58,468
Taxes other than income taxes	77,017	92,733
Interest	246	8,032
Sales contracts	934	5,114
Workers’ compensation	18,782	15,184
Asset retirement obligations	19,840	19,515
Other	14,193	6,194
Accrued Liabilities, Current	$ 184,161	$ 205,240

Debt and Financing Arrangements (Debt Outstanding) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Oct. 01, 2016
Debt Instrument [Line Items]
Debt issuance costs	$ (5,300)	$ (5,200)
Current maturities of debt	15,783	11,038
Long-term debt	310,134	351,841
Term loan due 2024 ($297.8 million face value) \| Loans payable
Debt Instrument [Line Items]
Amount of debt instrument	297,750
Term loan due 2021 ($325.7 million face value) \| Loans payable
Debt Instrument [Line Items]
Amount of debt instrument	325,700
Successor
Debt Instrument [Line Items]
Other	36,514
Debt issuance costs	(7,032)
Total	325,917
Current maturities of debt	15,783
Long-term debt	310,134
Successor \| Term loan due 2024 ($297.8 million face value)
Debt Instrument [Line Items]
Term loan	296,435
Successor \| Term loan due 2021 ($325.7 million face value)
Debt Instrument [Line Items]
Term loan	$ 0
Current maturities of debt			$ 3,300
Predecessor
Debt Instrument [Line Items]
Other		37,195
Debt issuance costs		0
Total		362,879
Current maturities of debt		11,038
Long-term debt		351,841
Predecessor \| Term loan due 2024 ($297.8 million face value)
Debt Instrument [Line Items]
Term loan		0
Predecessor \| Term loan due 2021 ($325.7 million face value)
Debt Instrument [Line Items]
Term loan		$ 325,684

Debt and Financing Arrangements (Company Debt Narrative) (Details) - USD ($)				3 Months Ended		9 Months Ended	12 Months Ended
	Sep. 25, 2017	Apr. 27, 2017	Mar. 07, 2017	Sep. 30, 2017	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt			$ 0		$ 0		$ (2,547,000)
Letters of credit outstanding							7,400,000
Additional availability for borrowings							1,100,000
Derivative Assets					74,155,000		55,550,000	$ 74,155,000
Debt financing costs					0		10,149,000
Senior notes \| New term loan debt facility
Debt Instrument [Line Items]
Amount of debt instrument	$ 300,000,000
Call premium	1.00%
Mandatory prepayment amount			100.00%
Default to indebtedness amount			$ 50,000,000
Default to surety, reclamation, or similar bonds securing obligations			50,000,000
Default to uninsured judgements			50,000,000
Uninsured losses or proceedings against minimum amount			50,000,000
Senior notes \| New term loan debt facility \| LIBOR
Debt Instrument [Line Items]
Applicable margin on interest rate	3.25%
Successor
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt					0		(2,547,000)
Debt financing costs					$ 0		10,100,000
Legal and advisory fees							2,500,000
Predecessor
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt						$ (2,213,000)			$ (27,910,000)
Debt financing costs						23,011,000			0
Legal and advisory fees						$ 2,200,000			$ 24,200,000
Predecessor \| Line of credit
Debt Instrument [Line Items]
Write off of deferred financing costs								$ 3,700,000
Line of credit \| Secured debt
Debt Instrument [Line Items]
Letters of credit outstanding							85,000,000
New term loan debt facility \| Senior notes
Debt Instrument [Line Items]
Amount of debt instrument			$ 300,000,000
Percent of face amount of debt issued			99.50%
Quarterly principal amortization payments			$ 750,000
Voting interests of directly owned subsidiaries			100.00%
Voting equity interests of directly owned foreign subsidiaries			65.00%
New term loan debt facility \| Senior notes \| LIBOR
Debt Instrument [Line Items]
Applicable margin on interest rate			4.00%	3.25%
New term loan debt facility \| Senior notes \| LIBOR \| Minimum
Debt Instrument [Line Items]
Applicable margin on interest rate	1.00%		1.00%
New term loan debt facility \| Senior notes \| Base rate
Debt Instrument [Line Items]
Applicable margin on interest rate	2.25%		3.00%
Regions Bank \| Line of credit \| Secured debt
Debt Instrument [Line Items]
Amount of debt instrument		$ 40,000,000
Maximum borrowing capacity							200,000,000
Current borrowing capacity		160,000,000
Liquidity amount minimum		$ 175,000,000
Letters of credit outstanding							29,000,000
Borrowing base percentage, coal inventory		85.00%
Borrowing base percentage, parts and supplies inventory		85.00%
Borrowing base, percentage of clause		35.00%
Percent of eligible cash		100.00%
Covenant amount		$ 250,000,000
Regions Bank \| Line of credit \| Secured debt \| LIBOR \| Minimum
Debt Instrument [Line Items]
Applicable margin on interest rate		2.25%
Regions Bank \| Line of credit \| Secured debt \| LIBOR \| Maximum
Debt Instrument [Line Items]
Borrowing base, percentage of clause		2.50%
Regions Bank \| Line of credit \| Secured debt \| Base rate \| Minimum
Debt Instrument [Line Items]
Applicable margin on interest rate		1.25%
Regions Bank \| Line of credit \| Secured debt \| Base rate \| Maximum
Debt Instrument [Line Items]
Applicable margin on interest rate		1.50%
Interest rate swap
Debt Instrument [Line Items]
Gain (loss) on interest rate swap							(100,000)
Interest rate swap \| Other noncurrent assets
Debt Instrument [Line Items]
Derivative Assets							$ 1,800,000

Debt and Financing Arrangements (Interest Rate Derivatives) (Details) $ in Millions	Dec. 31, 2017 USD ($)
June 30, 2017
Derivative [Line Items]
Notional Amount (in millions)	$ 250.0
Fixed Rate	1.372%
June 29, 2018
Derivative [Line Items]
Notional Amount (in millions)	$ 250.0
Fixed Rate	1.662%
June 28, 2019
Derivative [Line Items]
Notional Amount (in millions)	$ 200.0
Fixed Rate	1.952%
June 30, 2020
Derivative [Line Items]
Notional Amount (in millions)	$ 150.0
Fixed Rate	2.182%

Debt and Financing Arrangements (Predecessor Company Debt) (Details) - Predecessor $ in Thousands	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
2018	$ 16,809
2019	11,119
2020	11,442
2021	8,853
2022	3,130
Thereafter	282,911
Total	$ 334,264

Taxes (Narrative) (Details) - USD ($)	3 Months Ended	12 Months Ended
Taxes (Narrative) (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2018	Oct. 02, 2016	Oct. 01, 2016
Operating Loss Carryforwards [Line Items]
Cancellation of debt income						$ 3,414,000,000
Decrease in operating loss carryforwards							$ 3,185,000,000
Operating loss carryforwards	$ 980,200,000	$ 980,200,000
Annual limitation on operating loss use	29,800,000.0	29,800,000.0
Tax credit carryforwards	23,900,000	23,900,000
Increase (decrease) in valuation allowance		35,700,000	$ (1,289,000,000)	$ 865,100,000
Tax loss carryforwards	$ 271,405,000	271,405,000	376,293,000	1,135,000,000
Additional valuation allowance			1,185,000,000
Net deferred tax assets			1,022,000,000
Tax Cuts and Jobs Act of 2017, Income tax expense (benefit)		330,900,000
Repatriation of foreign earnings		1,500,000
Cumulative foreign earnings		$ 4,200,000
Sequestration reduction rate	6.60%	6.60%
Tax Cuts and Jobs Act of 2017, Income tax expense (benefit) related to valuation allowance	$ (22,400,000)
Tax Cuts and Jobs Act of 2017, Provisional income tax expense (benefit) related to change in limit on deductible for covered employees		$ 200,000
Estimated sequestration reduction	1,500,000
Valuation allowance	610,500,000	610,500,000
Reductions as a result of lapses in the statute of limitations		0	37,110,000	$ 37,100,000
Interest and penalties accrued related to unrecognized tax benefits	$ 600,000	$ 600,000	$ 500,000
Scenario, forecast
Operating Loss Carryforwards [Line Items]
Gross unrecognized tax benefits					$ 3,300,000
Alternative minimum tax credits
Operating Loss Carryforwards [Line Items]
Decrease in tax credit carryforwards							$ 76,000,000
Tax credit carryforwards						25,600,000
Capital loss carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards						64,500,000
Domestic tax authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards						$ 957,100,000

Taxes (Schedule of Components of Income Tax) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Deferred:
Provision for (benefit from) income taxes	$ 1,156		$ (35,255)
Successor
Current:
Federal	0		835
State	(252)		31
Total current	(252)		866
Deferred:
Federal	1,352		(36,162)
State	56		41
Total deferred	1,408		(36,121)
Provision for (benefit from) income taxes	$ 1,156		$ (35,255)
Predecessor
Current:
Federal		$ 0		$ 0
State		7		3
Total current		7		3
Deferred:
Federal		(4,720)		(329,393)
State		87		(43,990)
Total deferred		(4,633)		(373,383)
Provision for (benefit from) income taxes		$ (4,626)		$ (373,380)

Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Income Tax Examination [Line Items]
Provision for (benefit from) income taxes	$ 1,156		$ (35,255)
Successor
Income Tax Examination [Line Items]
Income tax provision (benefit) at statutory rate	12,112		71,118
Percentage depletion allowance	(4,292)		(31,255)
State taxes, net of effect of federal taxes	633		7,002
Reversal of cancellation of indebtedness income	0		0
Worthless stock deduction	0		0
Change in valuation allowance	(7,655)		(410,983)
Impact of Tax Cuts and Jobs Act of 2017	0		332,345
Other, net	358		(3,482)
Provision for (benefit from) income taxes	$ 1,156		$ (35,255)
Predecessor
Income Tax Examination [Line Items]
Income tax provision (benefit) at statutory rate		$ 433,109		$ (1,150,283)
Percentage depletion allowance		(3,681)		(19,035)
State taxes, net of effect of federal taxes		(46,122)		(76,445)
Reversal of cancellation of indebtedness income		(1,493,162)		0
Worthless stock deduction		(80,077)		0
Change in valuation allowance		1,185,326		865,146
Impact of Tax Cuts and Jobs Act of 2017		0		0
Other, net		(19)		7,237
Provision for (benefit from) income taxes		$ (4,626)		$ (373,380)

Taxes (Schedule of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Tax loss carryforwards	$ 271,405	$ 376,293	$ 1,135,000
Tax credit carryforwards	29,736	22,798
Investment in tax partnerships & corporations	308,653	604,914
Other	28,321	39,251
Gross deferred tax assets	638,115	1,043,256
Valuation allowance	(610,571)	(1,021,553)
Total deferred tax assets	27,544	21,703
Deferred tax liabilities:
Plant and equipment	3,674	7,332
Other	1,351	14,258
Total deferred tax liabilities	5,025	21,590
Net deferred tax asset	$ 22,519	$ 113

Taxes (Schedule of Gross Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning Balance	$ 7,455	$ 38,877	$ 34,709
Additions based on tax positions related to the current year	3,928	2,979	4,168
Additions for tax positions of prior years	0	2,709
Reductions as a result of lapses in the statute of limitations	0	(37,110)	(37,100)
Ending Balance	$ 11,383	$ 7,455	$ 38,877

Asset Retirement Obligations (Schedule of Asset Retirement Obligations) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Accretion expense	$ 7,634		$ 30,209
Current portion included in accrued expenses	(19,515)		(19,840)
Successor
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	354,326		356,742
Accretion expense	7,634		30,209
Obligations of divested operations	0		(12,569)
Adjustments to the liability from changes in estimates	0		(23,215)
Liabilities settled	(5,218)		(22,472)
Fresh start accounting adjustment	0		0
Ending Balance	356,742	$ 354,326	328,695
Current portion included in accrued expenses	(19,515)		(19,840)
Noncurrent liability	337,227		$ 308,855
Predecessor
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning Balance	$ 354,326	410,454
Accretion expense		24,321		$ 33,680
Obligations of divested operations		(14,702)
Adjustments to the liability from changes in estimates		3,003
Liabilities settled		(11,087)
Fresh start accounting adjustment		(57,663)
Ending Balance		354,326		$ 410,454
Current portion included in accrued expenses		(17,290)
Noncurrent liability		$ 337,036

Asset Retirement Obligations (Narrative) (Details) $ in Millions	Dec. 31, 2017 USD ($)
asset retirement obligations [Line Items]
Surety bonds outstanding	$ 31.2
Letters of credit outstanding	7.4
Cash collateral for surety bond	2.6
Asset retirement obligations
asset retirement obligations [Line Items]
Surety bonds outstanding	$ 531.7

Fair Value Measurements (Summary of Financial Assets and Liabilities Accounted for at Fair Value) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets:
Investments in marketable securities	$ 155,846	$ 90,209
Derivatives	5,508	4,908
Liabilities:
Derivatives	7,217	101
Successor
Assets:
Investments in marketable securities	155,846
Derivatives	7,339
Total assets	163,185
Liabilities:
Derivatives	7,217
Successor \| Level 1
Assets:
Investments in marketable securities	64,100
Derivatives	0
Total assets	64,100
Liabilities:
Derivatives	7,263
Successor \| Level 2
Assets:
Investments in marketable securities	91,746
Derivatives	1,985
Total assets	93,731
Liabilities:
Derivatives	26
Successor \| Level 3
Assets:
Derivatives	5,354
Total assets	5,354
Liabilities:
Derivatives	$ (72)
Predecessor
Assets:
Investments in marketable securities		90,209
Derivatives		4,908
Total assets		95,117
Liabilities:
Derivatives		101
Predecessor \| Level 1
Assets:
Investments in marketable securities		2,137
Derivatives		262
Total assets		2,399
Liabilities:
Derivatives		(8)
Predecessor \| Level 2
Assets:
Investments in marketable securities		88,072
Total assets		88,072
Liabilities:
Derivatives		0
Predecessor \| Level 3
Assets:
Derivatives		4,646
Total assets		4,646
Liabilities:
Derivatives		$ 109

Fair Value Measurements (Summary of Change in the Fair Values of Financial Instruments Categorized as Level 3) (Details) - Level 3 - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017
Successor
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 3,842		$ 4,537
Realized and unrealized (gains) losses recognized in earnings, net	926		(2,305)
Included in other comprehensive income	0		0
Purchases	1,225		4,910
Issuances	(34)		(535)
Settlements	(1,422)		(1,181)
Ending balance	4,537	$ 3,842	$ 5,426
Predecessor
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 3,842	2,432
Realized and unrealized (gains) losses recognized in earnings, net		(1,686)
Included in other comprehensive income		0
Purchases		5,021
Issuances		(488)
Settlements		(1,437)
Ending balance		$ 3,842

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Net unrealized gain related to level 3 instruments	$ 2.3
Fair value of senior notes and other long-term debt, including amounts classified as current	$ 336.1	$ 362.9

Capital Stock (Dividends) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2017
Equity [Abstract]
Dividends (in dollars per share)	$ 0.35	$ 0.35	$ 0.35	$ 0.00	$ 1.05
Amount (in thousands)	$ 7,606	$ 8,200	$ 8,563	$ 0	$ 24,369

(Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
(Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Oct. 31, 2017	Apr. 30, 2017
Equity [Abstract]
Authorized amount of share repurchase program	$ 500		$ 300
Incremental increase to authorized amount of share repurchase program		$ 200
Document Fiscal Year Focus	2017
Warrants exercised (in shares)	65,499
Warrants issued (in shares)	1,846,158

Capital Stock (Share repurchase activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2017
Equity [Abstract]
Number of Shares	1,058,381	2,208,133	710,701	0	3,977,215
Average Repurchase Price per Share (in dollars per share)	$ 79.73	$ 75.49	$ 71.82	$ 0.00	$ 75,960.00
Amount (in thousands)	$ 84,381	$ 166,685	$ 51,043	$ 0	$ 302,109

Stock-Based Compensation and Other Incentive Plans (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Document Fiscal Year Focus			2017
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 1.0		$ 10.4
Unrecognized share-based compensation expense			$ 32.4
Weighted-average period for recognition of unrecognized share-based compensation expense			3 years
Time Based Restricted Stock Units (RSUs) \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			1 year
Time Based Restricted Stock Units (RSUs) \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Performance Based Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Performance Based Restricted Stock Units (RSUs) \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility rate (percent)			50.00%
Performance Based Restricted Stock Units (RSUs) \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility rate (percent)			60.00%
2016 Omnibus Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for incentive plan (in shares)			3.0
Number of shares available for grant (in shares)			2.4
Long Term Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Requisite service period		3 years
Compensation expense	1.6	$ 7.2	$ 0.7	$ 7.9
Amounts unpaid under long term incentive plan	$ 13.9		$ 8.7

Stock-Based Compensation and Other Incentive Plans (Restricted Stock Unit Activity) (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Time Based Awards
Restricted Stock Common Shares
Outstanding at beginning of period (in shares) \| shares	159
Granted (in shares) \| shares	92
Forfeited (in shares) \| shares	(2)
Canceled (in shares) \| shares	(9)
Outstanding at end of period (in shares) \| shares	240
Weighted Average Grant Date Fair Value
Outstanding weighted average grant date fair value at beginning of period (in dollars per share) \| $ / shares	$ 78.60
Granted (in dollars per share) \| $ / shares	$ 81.91
Forfeited (in dollars per share) \| $ / shares	78.60
Canceled (in dollars per share) \| $ / shares	$ 78.60
Outstanding weighted average grant date fair value at end of period (in dollars per share) \| $ / shares	$ 79.87
Performance Based Awards
Restricted Stock Common Shares
Outstanding at beginning of period (in shares) \| shares	225
Granted (in shares) \| shares	86
Forfeited (in shares) \| shares	0
Canceled (in shares) \| shares	0
Outstanding at end of period (in shares) \| shares	311
Weighted Average Grant Date Fair Value
Outstanding weighted average grant date fair value at beginning of period (in dollars per share) \| $ / shares	$ 67.34
Granted (in dollars per share) \| $ / shares	$ 101.38
Forfeited (in dollars per share) \| $ / shares	0.00
Canceled (in dollars per share) \| $ / shares	$ 0.00
Outstanding weighted average grant date fair value at end of period (in dollars per share) \| $ / shares	$ 76.75

Workers' Compensation Expense (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Reimbursable liabilities	$ 20.3
Insurance receivable, current	3.3	$ 0.8
Insurance receivable, noncurrent	$ 17.0
Traumatic and other workers’ compensation claims
Defined Benefit Plan Disclosure [Line Items]
Risk-free interest rate	2.43%
Surety bonds and letters of credit outstanding	$ 123.0

Workers' Compensation Expense (Worker's Compensation Expense) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Successor
Accrued Workers' Compensation [Line Items]
Service cost	$ 1,583		$ 6,320
Interest cost	1,126		4,651
Net amortization	0		0
Successor \| Traumatic and other workers’ compensation claims
Accrued Workers' Compensation [Line Items]
Total workers’ compensation expense	5,871		14,179
Successor \| Total occupational disease
Accrued Workers' Compensation [Line Items]
Service cost	1,583		6,320
Interest cost	1,126		4,651
Total occupational disease	2,709		10,971
Successor \| Traumatic injury claims and assessments
Accrued Workers' Compensation [Line Items]
Traumatic injury claims and assessments	$ 3,162		$ 3,208
Predecessor
Accrued Workers' Compensation [Line Items]
Service cost		$ 3,465		$ 4,282
Interest cost		3,184		3,944
Net amortization		4,325		6,973
Predecessor \| Traumatic and other workers’ compensation claims
Accrued Workers' Compensation [Line Items]
Total workers’ compensation expense		17,602		31,980
Predecessor \| Total occupational disease
Accrued Workers' Compensation [Line Items]
Service cost		3,465
Interest cost		3,184
Total occupational disease		10,974		15,199
Predecessor \| Traumatic injury claims and assessments
Accrued Workers' Compensation [Line Items]
Traumatic injury claims and assessments		$ 6,628		$ 16,781

Workers' Compensation Expense (Occupational Disease Costs Activity and Assumptions) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Self Insurance Reserve [Roll Forward]
Curtailments		$ 3,600
Successor
Self Insurance Reserve [Roll Forward]
Service cost	$ 1,583			$ 6,320
Interest cost	1,126			4,651
Predecessor
Self Insurance Reserve [Roll Forward]
Service cost			$ 3,465		$ 4,282
Interest cost			3,184		3,944
Fresh start accounting adjustment			20,794
Occupational disease costs
Self Insurance Reserve [Roll Forward]
Beginning of period				111,159
End of period	111,159			122,426
Occupational disease costs \| Successor
Self Insurance Reserve [Roll Forward]
Beginning of period	119,710			111,159
Service cost	1,583			6,320
Interest cost	1,126			4,651
Curtailments	0			(5,433)
Actuarial (gain) loss	(9,675)			12,242
Benefit and administrative payments	(1,585)			(6,513)
Fresh start accounting adjustment	0			0
End of period	111,159		119,710	$ 122,426
Discount rate (percent)				3.66%
Occupational disease costs \| Predecessor
Self Insurance Reserve [Roll Forward]
Beginning of period	$ 119,710	$ 90,836	90,836
Service cost			3,465
Interest cost			3,184
Curtailments			4,156
Actuarial (gain) loss			0
Benefit and administrative payments			(3,728)
Fresh start accounting adjustment			21,797
End of period			$ 119,710		$ 90,836
Discount rate (percent)	4.31%		3.80%

Workers' Compensation Expense (Schedule of Amounts Recognized in Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2015
Accrued Workers' Compensation [Line Items]
Total obligations	$ 203,617	$ 199,752
Less amount included in accrued expenses	18,782	15,184
Noncurrent obligations	184,835	184,568
Occupational disease costs
Accrued Workers' Compensation [Line Items]
Occupational disease costs	122,426	111,159
Occupational disease costs \| Successor
Accrued Workers' Compensation [Line Items]
Occupational disease costs	122,426	111,159	$ 119,710
Occupational disease costs \| Predecessor
Accrued Workers' Compensation [Line Items]
Occupational disease costs			$ 119,710	$ 90,836
Traumatic and other workers’ compensation claims
Accrued Workers' Compensation [Line Items]
Occupational disease costs	$ 81,191	$ 88,593

Employee Benefit Plans (Schedule of Defined Benefit Plans Disclosures) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015	Oct. 02, 2016
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Curtailments		$ 3,600
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year				$ 274,225
Value of Plan Assets at end of year	$ 274,225			255,642
Pension Benefits
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year				252,278
Value of Plan Assets at end of year	252,278			240,028
Successor
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	1,583			6,320
Interest cost	1,126			4,651
Successor \| Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at beginning of year	341,427			313,629
Service cost	0			0
Interest cost	2,768			11,169
Divestitures (see Note 5 to the Consolidated Financial Statements)	0			(29,097)
Settlements	(135)			(1,532)
Curtailments	0			0
Benefits paid	(11,009)			(38,197)
Other-primarily actuarial (gain) loss	(19,422)			14,126
Fresh start accounting adjustment	0			0
Benefit Obligations at end of year	313,629		$ 341,427	270,098
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year	292,726			274,225
Actual return on plan assets	(7,899)			39,689
Employer contributions	407			429
Benefits paid	(11,009)			(38,197)
Divestitures	0			(20,504)
Value of Plan Assets at end of year	274,225		292,726	255,642
Accrued benefit cost	(39,404)			(14,456)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit (cost)				0		$ 0
Accumulated gain				16,178		6,751
Total not yet recognized as a component of net periodic benefit cost				16,178		6,751
BALANCE SHEET AMOUNTS
Current liability				(420)		(520)
Noncurrent liability				(14,036)		(38,884)
Liability, Defined Benefit Plan				(14,456)		(39,404)
Successor \| Other Postretirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at beginning of year	120,311			111,867
Service cost	180			671
Interest cost	978			4,150
Divestitures (see Note 5 to the Consolidated Financial Statements)	0			0
Settlements	0			0
Curtailments	0			(520)
Benefits paid	(1,962)			(8,152)
Other-primarily actuarial (gain) loss	(7,640)			2,503
Fresh start accounting adjustment	0			0
Benefit Obligations at end of year	111,867		120,311	110,519
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year	0			0
Actual return on plan assets	0
Employer contributions	1,962			8,152
Benefits paid	(1,962)			(8,152)
Divestitures	0			0
Value of Plan Assets at end of year	0		0	0
Accrued benefit cost	(111,867)			(110,519)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit (cost)				0		0
Accumulated gain				5,137		7,640
Total not yet recognized as a component of net periodic benefit cost				5,137		7,640
BALANCE SHEET AMOUNTS
Current liability				(8,150)		(10,422)
Noncurrent liability				(102,369)		(101,445)
Liability, Defined Benefit Plan				$ (110,519)		$ (111,867)
Predecessor
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost			3,465		$ 4,282
Interest cost			3,184		3,944
Fresh start accounting adjustment			20,794
Predecessor \| Pension Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at beginning of year	341,427	301,292	301,292
Service cost			0		9
Interest cost			9,338		14,604
Divestitures (see Note 5 to the Consolidated Financial Statements)			0
Settlements			0
Curtailments			454
Benefits paid			(8,699)
Other-primarily actuarial (gain) loss			0
Fresh start accounting adjustment			39,042
Benefit Obligations at end of year			341,427		301,292
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year	292,726	273,499	273,499
Actual return on plan assets			27,811
Employer contributions			115
Benefits paid			(8,699)
Divestitures			0
Value of Plan Assets at end of year			292,726		273,499
Accrued benefit cost			(48,701)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit (cost)			0
Accumulated gain			0
Total not yet recognized as a component of net periodic benefit cost			0
BALANCE SHEET AMOUNTS
Current liability			(420)
Noncurrent liability			(48,281)
Liability, Defined Benefit Plan			(48,701)
Predecessor \| Other Postretirement Benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit Obligations at beginning of year	120,311	103,460	103,460
Service cost			393		866
Interest cost			3,223		1,904
Divestitures (see Note 5 to the Consolidated Financial Statements)			0
Settlements			0
Curtailments			714
Benefits paid			(8,273)
Other-primarily actuarial (gain) loss			0
Benefit Obligations at end of year			120,311		103,460
CHANGE IN PLAN ASSETS
Value of Plan Assets at beginning of year	$ 0	$ 0	0
Actual return on plan assets			0
Employer contributions			8,273
Benefits paid			(8,273)
Divestitures			0
Value of Plan Assets at end of year			0		$ 0
Accrued benefit cost			(120,311)
ITEMS NOT YET RECOGNIZED AS A COMPONENT OF NET PERIODIC BENEFIT COST
Prior service credit (cost)			0
Accumulated gain			0
Total not yet recognized as a component of net periodic benefit cost			0
BALANCE SHEET AMOUNTS
Current liability			(8,352)
Noncurrent liability			(111,959)
Liability, Defined Benefit Plan			$ (120,311)

Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed			6.20%
Ultimate trend rate			4.50%
Effect of one percentage point increase on postretirement benefit obligation			$ 11.6
Effect of one percentage point increase on postretirement benefit cost			$ 0.4
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations (percent)			39.00%
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations (percent)			61.00%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation of pension plans	$ 313.6		$ 270.1
Pension Contributions			0.4
Other postretirement benefits payments	$ 3.5	$ 13.8	$ 18.0	$ 20.5

Employee Benefit Plans (Schedule of Net Benefit Costs) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Successor
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,583		$ 6,320
Interest cost	1,126		4,651
Successor \| Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0		0
Interest cost	2,768		11,169
Curtailments	0		0
Settlements	(135)		(1,532)
Expected return on plan assets	(4,770)		(16,498)
Amortization of prior service credits	0		0
Amortization of other actuarial losses (gains)	0		0
Total occupational disease	(2,137)		(6,861)
Successor \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	180		671
Interest cost	978		4,150
Curtailments	0		(520)
Settlements	0		0
Expected return on plan assets	0		0
Amortization of prior service credits	0		0
Amortization of other actuarial losses (gains)	0		0
Total occupational disease	$ 1,158		$ 4,301
Predecessor
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 3,465		$ 4,282
Interest cost		3,184		3,944
Predecessor \| Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost		0		9
Interest cost		9,338		14,604
Curtailments		454		0
Settlements		0		2,656
Expected return on plan assets		(13,623)		(20,367)
Amortization of prior service credits		0		0
Amortization of other actuarial losses (gains)		3,973		8,850
Total occupational disease		142		5,752
Predecessor \| Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost		393		866
Interest cost		3,223		1,904
Curtailments		(970)		0
Settlements		0		0
Expected return on plan assets		0		0
Amortization of prior service credits		(7,854)		(8,335)
Amortization of other actuarial losses (gains)		(849)		(2,109)
Total occupational disease		$ (6,057)		$ (7,674)

Employee Benefit Plans (Schedule of Assumptions Used to Calculate Benefit Obligations) (Details)	Dec. 31, 2017	Dec. 31, 2016	Oct. 01, 2016
Successor \| Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate		395.00%
Successor \| Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	349.00%	393.00%
Predecessor \| Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate			339.00%
Predecessor \| Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate			337.00%
Maximum \| Successor \| Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.49%
Minimum \| Successor \| Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.27%

Employee Benefit Plans (Schedule of Assumptions Used) (Details)			3 Months Ended				6 Months Ended		9 Months Ended	12 Months Ended
	Oct. 01, 2016	Dec. 31, 2015	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Successor \| Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	3.95%		3.39%							377.00%
Expected return on plan assets			685.00%							620.00%
Successor \| Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate			337.00%							385.00%
Predecessor \| Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate		4.60%		3.80%	4.41%	4.61%	4.59%	4.15%
Expected return on plan assets									685.00%		700.00%
Predecessor \| Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate											391.00%
Maximum \| Predecessor \| Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate									4.57%
Minimum \| Predecessor \| Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate									3.80%

Employee Benefit Plans (Schedule of Allocation of Plan Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	$ 255,642	$ 274,225
Other liabilities	(9,605)	(22,170)
Level 1
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	92,783	77,022
Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	128,645	156,015
Level 3
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	18,600	19,241
U.S. small-cap
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	5,064	13,520
U.S. small-cap \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	5,064	13,520
U.S. mid-cap
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	22,640	29,687
U.S. mid-cap \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	6,017	9,422
U.S. mid-cap \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	16,623	20,265
U.S. large-cap
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	43,232	70,226
U.S. large-cap \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	21,416	34,107
U.S. large-cap \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	21,816	36,119
Non-U.S.
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	10,115	18,937
Non-U.S. \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	10,115	18,937
U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	66,922	26,519
U.S. government securities \| Level 1
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	60,286	19,973
U.S. government securities \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	6,636	6,546
Non-U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	4,050	1,567
Non-U.S. government securities \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	4,050	1,567
U.S. governement asset and mortgage backed securities
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	2,440	1,074
U.S. governement asset and mortgage backed securities \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	2,440	1,074
Corporate fixed income
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	54,679	58,191
Corporate fixed income \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	54,679	58,191
State and local government securities
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	3,829	6,406
State and local government securities \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	3,829	6,406
Other investments
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	27,057	26,151
Other investments \| Level 2
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	8,457	6,910
Other investments \| Level 3
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	18,600	19,241
Other fixed income
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	16,646	35,519
Short-term investments
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	8,573	8,598
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total fair value of plan assets	$ 240,028	$ 252,278

Employee Benefit Plans (Summary of Estimated Future Benefit Payments) (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
2018	$ 17,614
2019	17,834
2020	18,174
2021	18,635
2022	19,235
Next 5 years	83,071
Total	174,563
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
2018	12,381
2019	12,549
2020	12,990
2021	13,239
2022	13,423
Next 5 years	62,854
Total	$ 127,436

Earnings (Loss) Per Common Share (Weighted Average Number of Shares) (Details) - shares shares in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Basic weighted average shares outstanding (in shares)	25,002		23,725
Diluted weighted average shares outstanding	25,469		24,240
Successor
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Basic weighted average shares outstanding (in shares)	25,002		23,725
Effect of dilutive securities	467		515
Diluted weighted average shares outstanding	25,469		24,240
Predecessor
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Basic weighted average shares outstanding (in shares)		21,293		21,285
Effect of dilutive securities		20		0
Diluted weighted average shares outstanding		21,313		21,285

Leases (Schedule of Lease Minimum Payments) (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Operating leases
lease payments [Line Items]
2018	$ 5,936
2019	4,655
2020	2,260
2021	1,985
2022	2,024
Thereafter	8,292
Total	25,152
Royalties
lease payments [Line Items]
2018	3,582
2019	5,926
2020	6,953
2021	7,216
2022	7,003
Thereafter	34,371
Total	$ 65,051

Leases (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
Leases (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Leases [Abstract]
Rental expense	$ 5.0	$ 19.4	$ 19.2	$ 28.4
Royalty expense	$ 45.3	$ 116.4	167.4	$ 227.7
Surety bonds outstanding			$ 31.2

Risk Concentrations (Narrative) (Details) $ in Thousands, T in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) T	Dec. 31, 2016 USD ($)
Concentration Risk [Line Items]
Trade accounts receivable	$ 172,604	$ 184,483
Tons of coal sold \| T	98.2
Percentage of tons sold under long term contract	66.00%
Long term contracts percentage of company revenue	55.00%
Long-term contracts, life term, minimum	1 year
Long-term contracts, life term, maximum	4 years
Electric utilities
Concentration Risk [Line Items]
Receivables	$ 72,900	$ 96,000
Percentage of total trade accounts receivable	42.00%	52.00%
Domestic and foreign steel producers
Concentration Risk [Line Items]
Trade accounts receivable	$ 99,400	$ 88,000
Trade receivables, percentage	58.00%	48.00%

Risk Concentrations (Schedule of Foreign Revenues) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Successor
foreign revenue [Line Items]
Revenues	$ 174,097		$ 793,594
Successor \| Europe
foreign revenue [Line Items]
Revenues	61,408		388,926
Successor \| Asia
foreign revenue [Line Items]
Revenues	55,634		264,503
Successor \| North America
foreign revenue [Line Items]
Revenues	43,831		88,145
Successor \| Central and South America
foreign revenue [Line Items]
Revenues	13,224		30,982
Successor \| Africa
foreign revenue [Line Items]
Revenues	0		14,901
Successor \| Brokered Sales
foreign revenue [Line Items]
Revenues	$ 0		$ 6,137
Predecessor
foreign revenue [Line Items]
Revenues		$ 280,879		$ 395,323
Predecessor \| Europe
foreign revenue [Line Items]
Revenues		113,888		170,314
Predecessor \| Asia
foreign revenue [Line Items]
Revenues		68,536		96,523
Predecessor \| North America
foreign revenue [Line Items]
Revenues		56,594		40,315
Predecessor \| Central and South America
foreign revenue [Line Items]
Revenues		41,861		55,323
Predecessor \| Africa
foreign revenue [Line Items]
Revenues		0		0
Predecessor \| Brokered Sales
foreign revenue [Line Items]
Revenues		$ 0		$ 32,848

Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Oct. 01, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Amount accrued			$ 0.2	$ 2.2
Amount accrued current portion			0.2	$ 2.2
2017			$ 97.2
Transportation capacity agreements	$ 1.6	$ 52.9

Subsequent Events (Details) - $ / shares		3 Months Ended				12 Months Ended
Subsequent Events (Details) - $ / shares	Feb. 13, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2017
Subsequent Event [Line Items]
Dividends (in dollars per share)		$ 0.35	$ 0.35	$ 0.35	$ 0.00	$ 1.05
Subsequent Event
Subsequent Event [Line Items]
Dividends (in dollars per share)	$ 0.40

Segment Information (Narrative) (Details)	12 Months Ended
Segment Information (Narrative) (Details)	Dec. 31, 2017 Segment
Segment Reporting [Abstract]
Distinct lines of business	2

Segment Information (Schedule of Operating Segment Results) (Details) - USD ($) $ in Thousands	3 Months Ended								9 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues					$ 575,688					$ 2,324,623
Depreciation, depletion and amortization					32,604					122,464
Accretion on asset retirement obligations					7,634					30,209
Assets	$ 1,979,632				2,136,597					1,979,632
Capital expenditures					15,214					59,205
Successor
Segment Reporting Information [Line Items]
Revenues	560,244				575,688					2,324,623
Adjusted EBITDAR					94,497					417,757
Depreciation, depletion and amortization					32,604					122,464
Accretion on asset retirement obligations					7,634					30,209
Assets					2,136,597
Capital expenditures					15,214					59,205
Successor \| Operating segments \| PRB
Segment Reporting Information [Line Items]
Revenues					275,703					1,024,197
Adjusted EBITDAR					55,765					158,882
Depreciation, depletion and amortization					9,949					36,349
Accretion on asset retirement obligations					5,049					20,160
Assets	390,665				446,775					390,665
Capital expenditures					934					6,212
Successor \| Operating segments \| MET
Segment Reporting Information [Line Items]
Revenues					200,377					887,839
Adjusted EBITDAR					30,819					243,616
Depreciation, depletion and amortization					18,287					70,896
Accretion on asset retirement obligations					528					2,000
Assets	548,476				576,793					548,476
Capital expenditures					13,329					32,678
Successor \| Operating segments \| Other Thermal
Segment Reporting Information [Line Items]
Revenues					97,382					396,504
Adjusted EBITDAR					31,159					102,006
Depreciation, depletion and amortization					3,911					13,588
Accretion on asset retirement obligations					540					2,161
Assets	134,397				129,602					134,397
Capital expenditures					684					11,901
Successor \| Corporate, Other and Eliminations
Segment Reporting Information [Line Items]
Revenues					2,226					16,083
Adjusted EBITDAR					(23,246)					(86,747)
Depreciation, depletion and amortization					457					1,631
Accretion on asset retirement obligations					1,517					5,888
Assets	$ 906,094				983,427					906,094
Capital expenditures					$ 267					$ 8,414
Predecessor
Segment Reporting Information [Line Items]
Revenues		$ 613,538	$ 549,866	$ 600,975		$ 550,305	$ 420,298	$ 428,106	$ 1,398,709		$ 2,573,260
Adjusted EBITDAR									87,303		283,797
Depreciation, depletion and amortization									191,581		379,345
Accretion on asset retirement obligations									24,321		33,680
Assets									2,123,829		5,041,881
Capital expenditures									82,434		119,024
Predecessor \| Operating segments \| PRB
Segment Reporting Information [Line Items]
Revenues									726,747		1,448,440
Adjusted EBITDAR									113,185		281,039
Depreciation, depletion and amortization									100,151		176,257
Accretion on asset retirement obligations									16,940		22,156
Assets									456,711		1,648,916
Capital expenditures									612		21,228
Predecessor \| Operating segments \| MET
Segment Reporting Information [Line Items]
Revenues									437,069		637,941
Adjusted EBITDAR									11,851		70,450
Depreciation, depletion and amortization									55,311		133,463
Accretion on asset retirement obligations									1,765		2,267
Assets									619,154		772,439
Capital expenditures									17,296		24,787
Predecessor \| Operating segments \| Other Thermal
Segment Reporting Information [Line Items]
Revenues									213,052		428,809
Adjusted EBITDAR									31,448		42,734
Depreciation, depletion and amortization									32,310		47,786
Accretion on asset retirement obligations									1,988		2,658
Assets									131,173		366,610
Capital expenditures									3,895		11,277
Predecessor \| Corporate, Other and Eliminations
Segment Reporting Information [Line Items]
Revenues									21,841		58,070
Adjusted EBITDAR									(69,181)		(110,426)
Depreciation, depletion and amortization									3,809		21,839
Accretion on asset retirement obligations									3,628		6,599
Assets									916,791		2,253,916
Capital expenditures									$ 60,631		$ 61,732

Segment Information (Reconciliation of Segment Income from Operations to Consolidated Income Before Income Taxes) (Details) - USD ($) $ in Thousands			3 Months Ended											6 Months Ended	9 Months Ended	12 Months Ended
	Mar. 07, 2017	Oct. 01, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2015	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Segment Reporting Information [Line Items]
Income (loss) before income taxes							$ 34,605									$ 203,195
Interest expense, net							10,754									24,256
Depreciation, depletion and amortization							32,604									122,464
Accretion on asset retirement obligations							7,634									30,209
Amortization of sales contracts, net							796									53,985
Asset impairment and mine closure costs							0				$ 500,000	$ 2,100,000	$ 19,100	$ 2,600,000		0
Losses from disposed operations resulting from Patriot Coal bankruptcy							0									0
Gain on sale of Lone Mountain Processing, Inc.							0									(21,297)
Net loss resulting from early retirement of debt and debt restructuring	$ 0						0									2,547
Successor
Segment Reporting Information [Line Items]
Income (loss) before income taxes							34,605									203,195
Interest expense, net							10,754									24,256
Depreciation, depletion and amortization							32,604									122,464
Accretion on asset retirement obligations							7,634									30,209
Amortization of sales contracts, net							796									53,985
Asset impairment and mine closure costs							0									0
Losses from disposed operations resulting from Patriot Coal bankruptcy							0									0
Gain on sale of Lone Mountain Processing, Inc.							0									(21,297)
Net loss resulting from early retirement of debt and debt restructuring							0									2,547
Reorganization items, net			$ (494)				759									2,398
Fresh start coal inventory fair value adjustment							7,345									0
Adjusted EBITDAR							94,497									$ 417,757
Predecessor
Segment Reporting Information [Line Items]
Income (loss) before income taxes															$ 1,237,455		$ (3,286,522)
Interest expense, net															133,235		393,549
Depreciation, depletion and amortization															191,581		379,345
Accretion on asset retirement obligations															24,321		33,680
Amortization of sales contracts, net															(728)		(8,811)
Asset impairment and mine closure costs								$ 46	$ 43,701	$ 85,520					129,267		2,628,303
Losses from disposed operations resulting from Patriot Coal bankruptcy															0		116,343
Gain on sale of Lone Mountain Processing, Inc.															0		0
Net loss resulting from early retirement of debt and debt restructuring															2,213		27,910
Reorganization items, net		$ (1,676,091)		$ 43	$ 21	$ 2,828	$ 759	$ 20,904	$ 21,271	$ 3,875					(1,630,041)		0
Fresh start coal inventory fair value adjustment															0		0
Adjusted EBITDAR															$ 87,303		$ 283,797

Quarterly Selected Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended											6 Months Ended	9 Months Ended	12 Months Ended
	Oct. 01, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2015	Oct. 01, 2016	Dec. 31, 2017	Dec. 31, 2015
Class of Stock [Line Items]
Revenues						$ 575,688									$ 2,324,623
Asset impairment and mine closure costs						0				$ 500,000	$ 2,100,000	$ 19,100	$ 2,600,000		0
Income (loss) from operations						46,118									232,396
Net income (loss)						$ 33,449									$ 238,450
Diluted earnings (loss) per common share (in dollars per share)						$ 1.31									$ 9.84
Predecessor
Class of Stock [Line Items]
Revenues			$ 613,538	$ 549,866	$ 600,975		$ 550,305	$ 420,298	$ 428,106					$ 1,398,709		$ 2,573,260
Gross profit			65,100	62,577	85,747		31,042	(56,469)	(53,325)
Asset impairment and mine closure costs							46	43,701	85,520					129,267		2,628,303
Income (loss) from operations			72,489	42,692	66,264		11,795	(110,521)	(158,412)					(257,138)		(2,865,063)
Reorganization items, net	$ 1,676,091		(43)	(21)	(2,828)	$ (759)	(20,904)	(21,271)	(3,875)					1,630,041		0
Net income (loss)	$ 1,676,091		$ 68,351	$ 37,160	$ 51,668		$ (51,421)	$ (175,887)	$ (206,702)					$ 1,242,081		$ (2,913,142)
Diluted earnings (loss) per common share (in dollars per share)	$ 78.66		$ 2.83	$ 1.48	$ 2.03		$ (2.41)	$ (8.26)	$ (9.71)					$ 58.28		$ (136.86)
Successor
Class of Stock [Line Items]
Revenues		$ 560,244				575,688									$ 2,324,623
Gross profit		62,937				64,458
Asset impairment and mine closure costs						0									0
Income (loss) from operations		50,951				46,118
Reorganization items, net		494				(759)									$ (2,398)
Net income (loss)		$ 81,271				$ 33,449
Diluted earnings (loss) per common share (in dollars per share)		$ 3.64				$ 1.31

Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2015
Reserves deducted from asset accounts:
Balance at End of Year		$ 610,500
Successor \| Accounts receivable and other receivables
Reserves deducted from asset accounts:
Balance at Beginning of Year	$ 0	0
Additions (Reductions) Charged to Costs and Expenses	0
Charged to Other Accounts	0
Deductions	0
Balance at End of Year	0	0
Successor \| Current assets — supplies and inventory
Reserves deducted from asset accounts:
Balance at Beginning of Year	0	0
Additions (Reductions) Charged to Costs and Expenses	0	365
Charged to Other Accounts	0	(17)
Deductions	0	87
Balance at End of Year	0	261
Successor \| Deferred income taxes
Reserves deducted from asset accounts:
Balance at Beginning of Year	1,033,982	1,021,553
Additions (Reductions) Charged to Costs and Expenses	(12,429)	(410,982)
Charged to Other Accounts	0
Deductions	0
Balance at End of Year	1,021,553	$ 610,571
Predecessor \| Accounts receivable and other receivables
Reserves deducted from asset accounts:
Balance at Beginning of Year	0		$ 159
Additions (Reductions) Charged to Costs and Expenses	0		7,683
Charged to Other Accounts	0		0
Deductions	7,842		0
Balance at End of Year			7,842
Predecessor \| Current assets — supplies and inventory
Reserves deducted from asset accounts:
Balance at Beginning of Year	0		6,625
Additions (Reductions) Charged to Costs and Expenses	844		431
Charged to Other Accounts	(5,060)		0
Deductions	1,775		1,065
Balance at End of Year			5,991
Predecessor \| Deferred income taxes
Reserves deducted from asset accounts:
Balance at Beginning of Year	1,033,982		270,251
Additions (Reductions) Charged to Costs and Expenses	(101,417)		865,148
Charged to Other Accounts			0
Deductions	$ 0		0
Balance at End of Year			$ 1,135,399