Alpha Metallurgical Resources (AMR) 10-Q 6 Aug 21 2021 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2021	Jul. 31, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2021
Document Transition Report	false
Entity File Number	001-38735
Entity Registrant Name	ALPHA METALLURGICAL RESOURCES, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-3015061
Entity Address, Address Line One	340 Martin Luther King Jr. Blvd.
Entity Address, City or Town	Bristol
Entity Address, State or Province	TN
Entity Address, Postal Zip Code	37620
City Area Code	423
Local Phone Number	573-0300
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock
Trading Symbol	AMR
Security Exchange Name	NYSE
Entity Common Stock, Shares Outstanding		18,400,317
Entity Central Index Key	0001704715
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Amendment Flag	false

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues:
Coal revenues	$ 393,458	$ 353,115	$ 778,910	$ 754,575
Other revenues	1,817	825	2,618	2,169
Total revenues	395,275	353,940	781,528	756,744
Costs and expenses:
Cost of coal sales (exclusive of items shown separately below)	346,763	335,267	694,191	669,487
Depreciation, depletion and amortization	27,304	47,069	55,742	94,685
Accretion on asset retirement obligations	6,648	6,569	13,296	13,208
Amortization of acquired intangibles, net	2,553	1,881	6,422	2,392
Asset impairment and restructuring	0	20,498	(561)	54,207
Selling, general and administrative expenses (exclusive of depreciation, depletion and amortization shown separately above)	14,645	12,028	29,627	27,509
Total other operating (income) loss:
Mark-to-market adjustment for acquisition-related obligations	3,157	(2,052)	6,333	(17,049)
Other income	(3,608)	(45)	(4,833)	(713)
Total costs and expenses	397,462	421,215	800,217	843,726
Loss from operations	(2,187)	(67,275)	(18,689)	(86,982)
Other (expense) income:
Interest expense	(17,962)	(19,316)	(35,952)	(37,492)
Interest income	104	5,530	268	6,498
Equity loss in affiliates	(384)	(1,047)	(518)	(1,790)
Miscellaneous income (loss), net	1,847	395	3,613	(321)
Total other expense, net	(16,395)	(14,438)	(32,589)	(33,105)
Loss from continuing operations before income taxes	(18,582)	(81,713)	(51,278)	(120,087)
Income tax (expense) benefit	(8)	(33)	(3)	2,155
Net loss from continuing operations	(18,590)	(81,746)	(51,281)	(117,932)
Discontinued operations:
Loss from discontinued operations before income taxes	(401)	(156,555)	(638)	(160,177)
Loss from discontinued operations	(401)	(156,555)	(638)	(160,177)
Net loss	$ (18,991)	$ (238,301)	$ (51,919)	$ (278,109)
Basic and diluted loss per common share:
Loss from continuing operations - basic (in dollars per share)	$ (1.01)	$ (4.47)	$ (2.78)	$ (6.45)
Loss from continuing operations - diluted (in dollars per share)reported (in dollars per share)	(1.01)	(4.47)	(2.78)	(6.45)
Loss from discontinued operations - basic (in dollars per share)	(0.02)	(8.55)	(0.04)	(8.77)
Loss from discontinued operations - diluted (in dollars per share)	(0.02)	(8.55)	(0.04)	(8.77)
Net loss - basic (in dollars per share)	(1.03)	(13.02)	(2.82)	(15.22)
Net loss - diluted (in dollars per share)	$ (1.03)	$ (13.02)	$ (2.82)	$ (15.22)
Weighted average shares - basic (in shares)	18,438,699	18,304,853	18,416,946	18,275,382
Weighted average shares - diluted (in shares)	18,438,699	18,304,853	18,416,946	18,275,382

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Other Comprehensive Income [Abstract]
Net loss	$ (18,991)	$ (238,301)	$ (51,919)	$ (278,109)
Employee benefit plans:
Amortization of and adjustments to employee benefit costs	10,180	(7,121)	11,664	(11,131)
Income tax expense	0	0	0	0
Total other comprehensive income (loss), net of tax	10,180	(7,121)	11,664	(11,131)
Total comprehensive loss	$ (8,811)	$ (245,422)	$ (40,255)	$ (289,240)

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 72,337	$ 139,227
Trade accounts receivable, net of allowance for doubtful accounts of $175 and $293 as of June 30, 2021 and December 31, 2020	206,693	145,670
Inventories, net	144,416	108,051
Prepaid expenses and other current assets	108,515	106,252
Current assets - discontinued operations	2,157	10,935
Total current assets	534,118	510,135
Property, plant, and equipment, net of accumulated depreciation and amortization of $418,677 and $382,423 as of June 30, 2021 and December 31, 2020	357,152	363,620
Owned and leased mineral rights, net of accumulated depletion and amortization of $45,505 and $35,143 as of June 30, 2021 and December 31, 2020	452,887	463,250
Other acquired intangibles, net of accumulated amortization of $32,286 and $25,700 as of June 30, 2021 and December 31, 2020	81,610	88,196
Long-term restricted cash	92,758	96,033
Other non-current assets	134,781	149,382
Non-current assets - discontinued operations	9,477	9,473
Total assets	1,662,783	1,680,089
Current liabilities:
Current portion of long-term debt	29,404	28,830
Trade accounts payable	97,938	58,413
Acquisition-related obligations – current	22,866	19,099
Accrued expenses and other current liabilities	154,067	140,406
Current liabilities - discontinued operations	7,101	12,306
Total current liabilities	311,376	259,054
Long-term debt	550,263	553,697
Acquisition-related obligations - long-term	11,972	20,768
Workers’ compensation and black lung obligations	231,029	230,081
Pension obligations	198,549	218,671
Asset retirement obligations	140,840	140,074
Deferred income taxes	483	480
Other non-current liabilities	28,444	28,072
Non-current liabilities - discontinued operations	27,496	29,090
Total liabilities	1,500,452	1,479,987
Commitments and Contingencies (Note 16)
Stockholders’ Equity
Preferred stock - par value $0.01, 5.0 million shares authorized, none issued	0	0
Common stock - par value $0.01, 50.0 million shares authorized, 20.8 million issued and 18.4 million outstanding at June 30, 2021 and 20.6 million issued and 18.3 million outstanding at December 31, 2020	208	206
Additional paid-in capital	782,586	779,424
Accumulated other comprehensive loss	(100,321)	(111,985)
Treasury stock, at cost: 2.4 million shares at June 30, 2021 and 2.3 million shares at December 31, 2020	(107,694)	(107,014)
Accumulated deficit	(412,448)	(360,529)
Total stockholders’ equity	162,331	200,102
Total liabilities and stockholders’ equity	$ 1,662,783	$ 1,680,089

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - Parenthetical - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 175	$ 293
Property, plant and equipment, accumulated amortization, depreciation and amortization	418,677	382,423
Owned and lease mineral rights, accumulated depletion and amortization	45,505	35,143
Other acquired intangibles, accumulated amortization	$ 32,286	$ 25,700
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, shares issued (in shares)	20,800,000	20,600,000
Common stock, shares outstanding (in shares)	18,400,000	18,300,000
Treasury stock, shares at cost (in shares)	2,400,000	2,300,000

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Operating activities:
Net loss	$ (51,919)	$ (278,109)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation, depletion and amortization	55,742	103,727
Amortization of acquired intangibles, net	6,422	2,961
Accretion of acquisition-related obligations discount	723	2,227
Amortization of debt issuance costs and accretion of debt discount	6,480	7,389
Mark-to-market adjustment for acquisition-related obligations	6,333	(17,049)
Gain on disposal of assets	(4,878)	(755)
Asset impairment and restructuring	(561)	217,882
Accretion on asset retirement obligations	13,296	14,679
Employee benefit plans, net	5,744	10,605
Deferred income taxes	3	33,032
Stock-based compensation	3,162	3,121
Equity loss in affiliates	518	1,790
Other, net	(220)	92
Changes in operating assets and liabilities	(66,296)	(22,654)
Net cash (used in) provided by operating activities	(25,451)	78,938
Investing activities:
Capital expenditures	(38,039)	(91,090)
Proceeds on disposal of assets	6,801	1,285
Purchases of investment securities	(15,470)	(18,607)
Maturity of investment securities	7,766	10,653
Capital contributions to equity affiliates	(1,895)	(2,416)
Other, net	35	47
Net cash used in investing activities	(40,802)	(100,128)
Financing activities:
Proceeds from borrowings on debt	0	57,500
Principal repayments of debt	(6,159)	(29,559)
Principal repayments of notes payable	(1,362)	(574)
Principal repayments of financing lease obligations	(1,002)	(1,614)
Debt issuance costs	(226)	0
Common stock repurchases and related expenses	(680)	(155)
Net cash (used in) provided by financing activities	(9,429)	25,598
Net (decrease) increase in cash and cash equivalents and restricted cash	(75,682)	4,408
Cash and cash equivalents and restricted cash at beginning of period	244,571	347,680
Cash and cash equivalents and restricted cash at end of period	168,889	352,088
Reconciliation of Cash and Cash Equivalents and Restricted Cash
Cash and cash equivalents	72,337	238,438
Short-term restricted cash (included in prepaid expenses and other current assets)	3,794	3,720
Long-term restricted cash	92,758	109,930
Total cash and cash equivalents and restricted cash shown in the Condensed Consolidated Statements of Cash Flows	$ 168,889	$ 352,088

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Cumulative effect	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Treasury Stock at Cost	Retained Earnings (Deficit)	Retained Earnings (Deficit)Cumulative effect
Beginning balance at Dec. 31, 2019	$ 696,122	$ (440)	$ 205	$ 775,707	$ (58,616)	$ (107,984)	$ 86,810	$ (440)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(39,808)						(39,808)
Other comprehensive loss, net	(4,010)				(4,010)
Stock-based compensation and net issuance of common stock for share vesting	900			900
Common stock reissuances, repurchases and related expenses	1,071					1,071
Ending balance at Mar. 31, 2020	653,835		205	776,607	(62,626)	(106,913)	46,562
Beginning balance at Dec. 31, 2019	696,122	$ (440)	205	775,707	(58,616)	(107,984)	86,810	$ (440)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(278,109)
Other comprehensive loss, net	(11,131)
Ending balance at Jun. 30, 2020	409,415		206	777,650	(69,747)	(106,955)	(191,739)
Beginning balance at Mar. 31, 2020	653,835		205	776,607	(62,626)	(106,913)	46,562
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(238,301)						(238,301)
Other comprehensive loss, net	(7,121)				(7,121)
Stock-based compensation and net issuance of common stock for share vesting	1,044		1	1,043
Common stock reissuances, repurchases and related expenses	(42)					(42)
Ending balance at Jun. 30, 2020	409,415		206	777,650	(69,747)	(106,955)	(191,739)
Beginning balance at Dec. 31, 2020	200,102		206	779,424	(111,985)	(107,014)	(360,529)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(32,928)						(32,928)
Other comprehensive loss, net	1,484				1,484
Stock-based compensation and net issuance of common stock for share vesting	2,183		1	2,182
Common stock reissuances, repurchases and related expenses	(680)					(680)
Ending balance at Mar. 31, 2021	170,161		207	781,606	(110,501)	(107,694)	(393,457)
Beginning balance at Dec. 31, 2020	200,102		206	779,424	(111,985)	(107,014)	(360,529)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(51,919)
Other comprehensive loss, net	11,664
Ending balance at Jun. 30, 2021	162,331		208	782,586	(100,321)	(107,694)	(412,448)
Beginning balance at Mar. 31, 2021	170,161		207	781,606	(110,501)	(107,694)	(393,457)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(18,991)						(18,991)
Other comprehensive loss, net	10,180				10,180
Stock-based compensation and net issuance of common stock for share vesting	981		1	980
Ending balance at Jun. 30, 2021	$ 162,331		$ 208	$ 782,586	$ (100,321)	$ (107,694)	$ (412,448)

Business and Basis of Presentat

Business and Basis of Presentation	6 Months Ended
	Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business and Basis of Presentation	Business and Basis of Presentation Business Alpha Metallurgical Resources, Inc. (“Alpha” or the “Company”) is a Tennessee-based mining company with operations across Virginia and West Virginia. With customers across the globe, high-quality reserves and significant port capacity, Alpha is a leading U.S. supplier of metallurgical products for the steel industry. Basis of Presentation Together, the condensed consolidated statements of operations, comprehensive loss, balance sheets, cash flows and stockholders’ equity for the Company are referred to as the “Condensed Consolidated Financial Statements.” The Condensed Consolidated Financial Statements are also referenced across periods as “Condensed Consolidated Statements of Operations,” “Condensed Consolidated Statements of Comprehensive Loss,” “Condensed Consolidated Balance Sheets,” “Condensed Consolidated Statements of Cash Flows,” and “Condensed Consolidated Statements of Stockholders’ Equity.” The Company’s former Northern Appalachia (“NAPP”) operations results of operations and financial position are reported as discontinued operations in the Condensed Consolidated Financial Statements. The historical information in the accompanying Notes to the Condensed Consolidated Financial Statements has been restated to reflect the effects of the Company’s former NAPP operations being reported as discontinued operations in the Condensed Consolidated Financial Statements. Refer to Note 2 for further information on discontinued operations. The Condensed Consolidated Financial Statements include all wholly-owned subsidiaries’ results of operations for the three and six months ended June 30, 2021 and 2020. All significant intercompany transactions have been eliminated in consolidation. The accompanying interim Condensed Consolidated Financial Statements are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) and in accordance with the rules and regulations of the United States Securities and Exchange Commission (“SEC”) for Form 10-Q. Such rules and regulations allow the omission of certain information and footnote disclosures normally included in the financial statements prepared in accordance with U.S. GAAP as long as the financial statements are not misleading. In the opinion of management, these interim Condensed Consolidated Financial Statements reflect all normal and recurring adjustments necessary for a fair presentation of the results for the periods presented. Results of operations for the three and six months ended June 30, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021 or any other period. These interim Condensed Consolidated Financial Statements should be read in conjunction with the Company’s Consolidated Financial Statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020. Liquidity Risks and Uncertainties The Company believes it will have sufficient liquidity to meet its working capital requirements, anticipated capital expenditures, debt service requirements, acquisition-related obligations, and reclamation obligations for the 12 months subsequent to the issuance of these financial statements. However, the Company may need to raise additional funds if market conditions deteriorate and may not be able to do so in a timely fashion, or at all. The Company relies on a number of assumptions in budgeting for future activities. These include the costs for mine development to sustain capacity of its operating mines, cash flows from operations, effects of regulation and taxes by governmental agencies, mining technology improvements and reclamation costs. These assumptions are inherently subject to significant business, political, economic, regulatory, environmental and competitive uncertainties, contingencies and risks, all of which are difficult to predict and many of which are beyond the Company’s control. Therefore, the Company’s cash on hand and from future operations will be subject to any significant changes in these assumptions. COVID-19 Pandemic In the first quarter of 2020, the COVID-19 virus was declared a pandemic by the World Health Organization. The COVID-19 pandemic has had negative impacts on the Company’s business, results of operations, financial condition and cash flows. The full extent of the impact of the COVID-19 pandemic on the Company’s operational and financial performance will depend on certain developments, including the duration and spread of the outbreak, its impact on its customers and suppliers and the range of governmental and community reactions to the pandemic, which are still uncertain and still cannot be fully predicted. Recently Adopted Accounting Guidance Convertible Debt and Contracts in Entity’s Own Equity : In August 2020, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40) (“ASU 2020-06”). The amendments in this update simplify the accounting for certain financial instruments with characteristics of liabilities and equity, including convertible instruments and contracts in an entity’s own equity, such as the Company’s outstanding Series A warrants. For public business entities, the standard is effective for fiscal years beginning after December 15, 2021, with early adoption permitted. The Company adopted ASU 2020-06 during the first quarter of 2021. The adoption of this ASU did not have a material impact on the Company's Condensed Consolidated Financial Statements and related disclosures. Reference Rate Reform : In January 2021, the FASB issued ASU 2021-01, Reference Rate Reform (Topic 848) (“ASU 2021-01”). The amendments in this update clarify that certain optional expedients and exceptions in Topic 848 for contract modifications and hedge accounting apply to derivatives that are affected by the discounting transition. For all entities, the standard is effective immediately. The Company adopted ASU 2021-01 during the first quarter of 2021. The adoption of this ASU did not have a material impact on the Company's Condensed Consolidated Financial Statements and related disclosures. Certain Modifications or Exchanges of Freestanding Equity-Classified Written Call Options: In May 2021, the FASB issued ASU 2021-04, Earnings Per Share (Topic 260), Debt—Modifications and Extinguishments (Subtopic 470-50), Compensation—Stock Compensation (Topic 718), and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40)

Discontinued Operations

Discontinued Operations	6 Months Ended
	Jun. 30, 2021
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	Discontinued Operations Discontinued operations consist of activity related to the Company’s former NAPP operations. On December 10, 2020, the Company closed on a transaction to sell its thermal coal mining operations located in Pennsylvania consisting primarily of its Cumberland mining complex and related property to a third party purchaser, Iron Senergy Holdings, LLC (“Iron Senergy”). The mining permits associated with the Cumberland operations were obtained by Iron Senergy at closing. During the second quarter of 2021, nearly all of the Company’s remaining surety bonds were released and Iron Senergy’s replacement bonds were accepted through the administrative process with only $30 remaining and expected to be released in the short-term. Major Financial Statement Components of Discontinued Operations The loss from discontinued operations before income taxes for the three and six months ended June 30, 2021 was $401 and $638, respectively. The major components of loss from discontinued operations before income taxes in the Condensed Consolidated Statements of Operations for the three and six months ended June 30, 2020 are as follows: Three Months Ended June 30, 2020 (1) Six Months Ended June 30, 2020 (1) Revenues: Total revenues $ 57,898 $ 125,554 Costs and expenses: Cost of coal sales (exclusive of items shown separately below) 47,843 110,265 Depreciation, depletion and amortization 2,193 9,042 Accretion on asset retirement obligations 735 1,471 Selling, general and administrative expenses (2) 169 1,387 Asset impairment and restructuring (3) 163,675 163,675 Other non-major income items, net (162) (109) Loss from discontinued operations before income taxes $ (156,555) $ (160,177) (1) Includes minor residual activity related to the Company’s former Powder River Basin (“PRB”) operations. (2) Represents professional and legal fees. (3) Refer to Note 8 for additional information on asset impairment and restructuring during the periods. Refer to the Condensed Consolidated Statements of Operations for loss per share information related to discontinued operations. The major components of assets and liabilities that are classified as discontinued operations in the Condensed Consolidated Balance Sheets are as follows: June 30, 2021 December 31, 2020 Assets: Trade accounts receivable, net of allowance for doubtful accounts $ — $ 7,504 Prepaid expenses and other current assets $ 2,157 $ 3,431 Other non-current assets (1) $ 9,477 $ 9,473 Liabilities: Trade accounts payable, accrued expenses and other current liabilities $ 7,101 $ 12,306 Workers’ compensation and black lung obligations, non-current $ 26,205 $ 27,799 Other non-current liabilities $ 1,291 $ 1,291 (1) Primarily comprised of workers’ compensation insurance receivable and long-term restricted investments collateralizing workers’ compensation obligations. The major components of cash flows related to discontinued operations are as follows: Six Months Ended June 30, 2020 Depreciation, depletion and amortization $ 9,042 Capital expenditures $ 24,169 Other significant operating non-cash items related to discontinued operations: Accretion on asset retirement obligations $ 1,471 Asset impairment and restructuring $ 163,675

Revenue

Revenue	6 Months Ended
	Jun. 30, 2021
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Disaggregation of Revenue from Contracts with Customers The Company earns revenues primarily through the sale of coal produced at Company operations and coal purchased from third parties. The Company extracts, processes and markets met and thermal coal from deep and surface mines for sale to steel and coke producers, industrial customers, and electric utilities. The Company has disaggregated revenue between met coal and thermal coal and export and domestic revenues which depicts the pricing and contract differences between the two. Export revenue generally is derived by spot or short term contracts with pricing determined at the time of shipment or based on a market index; whereas domestic revenue is characterized by contracts that typically have a term of one year or longer and typically the pricing is fixed. The following tables disaggregate the Company’s coal revenues by product category and by market to depict how the nature, amount, timing, and uncertainty of the Company’s coal revenues and cash flows are affected by economic factors: Three Months Ended June 30, 2021 Met Coal Thermal Coal Total Export coal revenues $ 250,324 $ 5,693 $ 256,017 Domestic coal revenues 105,235 32,206 137,441 Total coal revenues $ 355,559 $ 37,899 $ 393,458 Three Months Ended June 30, 2020 Met Coal Thermal Coal Total Export coal revenues $ 230,293 $ 10,369 $ 240,662 Domestic coal revenues 82,903 29,550 112,453 Total coal revenues $ 313,196 $ 39,919 $ 353,115 Six Months Ended June 30, 2021 Met Thermal Total Export coal revenues $ 493,076 $ 6,724 $ 499,800 Domestic coal revenues 205,477 73,633 279,110 Total coal revenues $ 698,553 $ 80,357 $ 778,910 Six Months Ended June 30, 2020 Met Thermal Total Export coal revenues $ 474,364 $ 17,752 $ 492,116 Domestic coal revenues 197,591 64,868 262,459 Total coal revenues $ 671,955 $ 82,620 $ 754,575 Performance Obligations The following table includes estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied as of June 30, 2021: Remainder of 2021 2022 2023 2024 2025 Total Estimated coal revenues $ 65,852 $ 50,935 $ — $ — $ — $ 116,787

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss The following tables summarize the changes to accumulated other comprehensive loss during the six months ended June 30, 2021 and 2020: Balance January 1, 2021 Other comprehensive income before reclassifications Amounts reclassified from accumulated other comprehensive loss Balance June 30, 2021 Employee benefit costs $ (111,985) $ 8,838 $ 2,826 $ (100,321) Balance January 1, 2020 Other comprehensive loss before reclassifications Amounts reclassified from accumulated other comprehensive loss Balance June 30, 2020 Employee benefit costs $ (58,616) $ (14,154) $ 3,023 $ (69,747) The following table summarizes the amounts reclassified from accumulated other comprehensive loss and the Condensed Consolidated Statements of Operations line items affected by the reclassification during the three and six months ended June 30, 2021 and 2020: Details about accumulated other comprehensive loss components Amounts reclassified from accumulated other comprehensive loss Affected line item in the Condensed Consolidated Statements of Operations Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Employee benefit costs: Amortization of net actuarial loss (1) $ 1,342 $ 934 $ 2,826 $ 1,728 Miscellaneous income (loss), net Settlement (1) — 95 — 1,295 Miscellaneous income (loss), net Total before income tax $ 1,342 $ 1,029 $ 2,826 $ 3,023 Income tax — — — — Income tax (expense) benefit Total, net of income tax $ 1,342 $ 1,029 $ 2,826 $ 3,023 (1) These accumulated other comprehensive loss components are included in the computation of net periodic benefit costs for certain employee benefit plans. Refer to Note 14.

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share The number of shares used to calculate basic net loss per common share is based on the weighted average number of the Company’s outstanding common shares during the respective period. The number of shares used to calculate diluted net loss per common share is based on the number of common shares used to calculate basic net loss per common share plus the dilutive effect of stock options and other stock-based instruments held by the Company’s employees and directors during the period, and the Company’s outstanding Series A warrants. The dilutive effect of outstanding stock-based instruments is determined by application of the treasury stock method. The warrants become dilutive for diluted net loss per common share calculations when the market price of the Company’s common stock exceeds the exercise price. As discussed below, dilutive securities are not included in the computation of diluted net loss per common share as the impact would be anti-dilutive. Refer to the Condensed Consolidated Statements of Operations for net loss per common share for the three and six months ended June 30, 2021 and 2020. For the three months ended June 30, 2021 and 2020, 942,549 and 1,581,608 warrants, stock options, and other stock-based instruments, respectively, were excluded from the computation of dilutive net loss per common share because they would have been anti-dilutive. For the six months ended June 30, 2021 and 2020, 948,398 and 1,492,657 warrants, stock options, and other stock-based instruments, respectively, were excluded from the computation of dilutive net loss per common share because they would have been anti-dilutive. When applying the treasury stock method, anti-dilution generally occurs when the exercise prices or unrecognized compensation cost per share are higher than the Company’s average stock price during an applicable period.

Inventories, net

Inventories, net	6 Months Ended
	Jun. 30, 2021
Inventory Disclosure [Abstract]
Inventories, net	Inventories, net Inventories, net consisted of the following: June 30, 2021 December 31, 2020 Raw coal $ 21,071 $ 15,084 Saleable coal 96,768 69,262 Materials, supplies and other, net 26,577 23,705 Total inventories, net $ 144,416 $ 108,051

Acquired Intangibles

Acquired Intangibles	6 Months Ended
	Jun. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Acquired Intangibles	Acquired Intangibles The Company has recognized assets for acquired above market-priced coal supply agreements and acquired mine permits and liabilities for acquired below market-priced coal supply agreements. The balances and respective balance sheet classifications of such assets and liabilities as of June 30, 2021 and December 31, 2020, net of accumulated amortization, are set forth in the following tables: June 30, 2021 Assets (1) Liabilities (2) Net Total Coal supply agreements, net $ — $ (163) $ (163) Acquired mine permits, net 81,610 — 81,610 Total $ 81,610 $ (163) $ 81,447 December 31, 2020 Assets (1) Liabilities (2) Net Total Coal supply agreements, net $ — $ (327) $ (327) Acquired mine permits, net 88,196 — 88,196 Total $ 88,196 $ (327) $ 87,869 (1) Included within other acquired intangibles, net of accumulated amortization on the Company’s Condensed Consolidated Balance Sheets. (2) Included within other non-current liabilities on the Company’s Condensed Consolidated Balance Sheets. The following table details the amortization of the Company’s acquired intangibles included within amortization of acquired intangibles, net in the Condensed Consolidated Statements of Operations: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Amortization of mine permits $ 2,635 $ 3,320 $ 6,586 $ 6,648 Amortization of above-market coal supply agreements $ — $ — $ — $ 18 Amortization of below-market coal supply agreements (82) (1,439) (164) (4,274) Net income $ (82) $ (1,439) $ (164) $ (4,256)

Asset Impairment and Restructur

Asset Impairment and Restructuring	6 Months Ended
	Jun. 30, 2021
Restructuring and Related Activities [Abstract]
Asset Impairment and Restructuring	Asset Impairment and Restructuring Long-lived Asset Impairment During the six months ended June 30, 2021, long-lived asset impairment of $60 was recorded in the All Other category to reduce the carrying value of property, plant, and equipment, net, due to capital spending during the period at previously impaired locations requiring the impairment of certain additional assets not considered recoverable. During the second quarter of 2020, as a result of the weakening coal market conditions due in part to the impact of the global COVID-19 pandemic, the Company announced that it would take certain strategic actions with respect to two of its thermal coal mining complexes in an effort to strengthen its financial performance and improve forecasted liquidity. The Company announced that an underground mine and preparation plant located in West Virginia would be idled during the third quarter of 2020. In addition, the Company decided not to move forward with the construction of a new refuse impoundment at its Cumberland mine in Pennsylvania and would therefore no longer spend the significant capital required in connection with the project. As a result, the Cumberland mine was expected to cease production by the end of 2022. On December 10, 2020, the Company sold its Cumberland mining operations. Refer to Note 2 for further details. In connection with the preparation of the Company’s financial statements for the quarter ended June 30, 2020, the Company determined that the strategic actions taken by the Company during the three months ended June 30, 2020, discussed above, shortened the lives of two mining complexes, and that continued weakening in metallurgical and thermal coal pricing had resulted in forecasted margins at certain locations falling below amounts necessary for full recoverability. As a result of these determinations, the Company assessed that indicators of impairment were present for three long-lived asset groups within its Met reporting segment and four long-lived asset groups within its All Other category. The Company therefore performed impairment testing on these assets and determined that, as of May 31, 2020, the carrying amounts of the asset groups exceeded both their undiscounted cash flows and their estimated fair values. The Company estimated the fair value of these asset groups generally using a discounted cash flow analysis utilizing market-participant assumptions. During the first quarter of 2020, due to declines in metallurgical and thermal coal pricing which reduced forecasted margins at certain locations to amounts below those required for full recoverability, the Company determined that indicators of impairment were present for four long-lived asset groups within its Met reporting segment and three long-lived asset groups within its All Other category and performed impairment testing as of February 29, 2020. At February 29, 2020, the Company determined that the carrying amounts of the asset groups exceeded both their undiscounted cash flows and their estimated fair values. The Company estimated the fair value of these asset groups generally using a discounted cash flow analysis utilizing market-participant assumptions. The following tables present the details of the long-lived asset impairment during the three and six months ended June 30, 2020: Three Months Ended June 30, 2020 Six Months Ended June 30, 2020 Continuing operations: Met $ — $ 32,951 All Other 17,390 18,148 Total from continuing operations $ 17,390 $ 51,099 Discontinued operations: $ 144,348 $ 144,348 Total long-lived asset impairment: $ 161,738 $ 195,447 Three Months Ended June 30, 2020 Six Months Ended June 30, 2020 Continuing operations: Mineral rights, net $ 2,241 $ 24,066 Property, plant, and equipment, net 6,496 12,562 Acquired mine permits, net 8,653 14,471 Total from continuing operations $ 17,390 $ 51,099 Discontinued operations: Mineral rights, net $ 16,364 $ 16,364 Property, plant, and equipment, net 127,984 127,984 Total from discontinued operations $ 144,348 $ 144,348 Total long-lived asset impairment: Mineral rights, net $ 18,605 $ 40,430 Property, plant, and equipment, net 134,480 140,546 Acquired mine permits, net 8,653 14,471 Total long-lived asset impairment $ 161,738 $ 195,447 Restructuring As a result of the strategic actions announced in the second quarter of 2020 and subsequent changes to severance and employee-related benefits, the Company recorded restructuring expense of ($621) in the All Other category during the six months ended June 30, 2021. As a result of the strategic actions discussed above, the Company recorded restructuring expense during the three and six months ended June 30, 2020 as follows: Three and Six Months Ended June 30, 2020 Total Restructuring Continuing Operations (3) Discontinued Operations Severance and employee-related benefits (1) $ 20,553 $ 2,301 $ 18,252 Other costs (2) 1,882 807 1,075 Total restructuring expense $ 22,435 $ 3,108 $ 19,327 (1) Severance and employee-related benefits were considered probable and estimable based on provisions of contractual agreements and existing employee benefit plans. (2) Includes accelerated amortization of deferred longwall move expenses of $668, allowance for advanced mining royalties of $407, and allowance for obsolete materials and supplies inventory of $807.

Long-Term Debt

Long-Term Debt	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term Debt Long-term debt consisted of the following: June 30, 2021 December 31, 2020 Term Loan Credit Facility - due June 2024 $ 550,564 $ 553,373 ABL Facility - due April 2022 — 3,350 LCC Note Payable 27,500 27,500 LCC Water Treatment Obligation 6,250 6,875 Other (1) 6,665 8,475 Debt discount and issuance costs (11,312) (17,046) Total long-term debt 579,667 582,527 Less current portion (29,404) (28,830) Long-term debt, net of current portion $ 550,263 $ 553,697 (1) Includes financing leases. Term Loan Credit Facility - due June 2024 As of June 30, 2021, the borrowings made under the senior secured term loan facility with a maturity date of June 14, 2024 (the “Term Loan Credit Facility”) were comprised of Eurocurrency Rate Loans (as defined therein) with an interest rate of 10.00%, calculated as the Eurocurrency rate during the period plus an applicable rate of 8.00%. As of June 30, 2021, the carrying value of the Term Loan Credit Facility was $541,572, with $5,618 classified as current within the Condensed Consolidated Balance Sheets. As of December 31, 2020, the carrying value of the Term Loan Credit Facility was $540,643, with $5,618 classified as current within the Condensed Consolidated Balance Sheets. All obligations under the Term Loan Credit Facility are guaranteed by substantially all of Alpha’s direct and indirect subsidiaries. Certain obligations under the Term Loan Facility are secured by a senior lien, subject to certain exceptions (including the ABL Priority Collateral described below), by substantially all of Alpha’s assets and the assets of Alpha’s subsidiary guarantors (“Term Loan Priority Collateral”), in each case subject to exceptions. The obligations under the Term Loan Credit Facility are also secured by a junior lien, again subject to certain exceptions, against the ABL Priority Collateral. The Term Loan Facility contains negative and affirmative covenants including certain financial covenants that are more flexible than the covenants in the Amended and Restated Credit Agreement dated November 9, 2018. The Company was in compliance with all covenants under this agreement as of June 30, 2021. Amended and Restated Asset-Based Revolving Credit Agreement The Amended and Restated Asset-Based Revolving Credit Agreement includes a senior secured asset-based revolving credit facility (the “ABL Facility”). Under the ABL Facility, the Company may borrow cash or obtain letters of credit, on a revolving basis. As of June 30, 2021, there were no outstanding borrowings under the ABL Facility. As of December 31, 2020, the carrying value of the ABL Facility was $3,350, all of which was classified as long-term within the Condensed Consolidated Balance Sheets. As of June 30, 2021 and December 31, 2020, the Company had $128,752 and $123,108 letters of credit outstanding under the ABL Facility, respectively. The Amended and Restated Asset-Based Revolving Credit Agreement provides that a specified percentage of billed, unbilled and approved foreign receivables and raw and clean inventory meeting certain criteria are eligible to be counted for purposes of collateralizing the amount of financing available, subject to certain terms and conditions. Availability under the ABL Facility is calculated on a monthly basis and fluctuates based on qualifying amounts of coal inventory and trade accounts receivable (the “Borrowing Base”) and the facility's covenant limitations related to the Fixed Charge Coverage Ratio (as defined therein). In accordance with terms of the ABL Facility, the Company may be required to collateralize the ABL Facility to the extent outstanding borrowings and letters of credit under the ABL Facility exceed the Borrowing Base after considering covenant limitations. The ABL Facility is guaranteed by substantially all of Alpha’s direct and indirect subsidiaries (together with Alpha, the “Loan Parties”) and secured by all or substantially all assets of the Loan Parties, including equity in Alpha’s direct domestic subsidiaries and first-tier foreign subsidiaries, as collateral for the obligations under the ABL Facility. The ABL Facility has a

Acquisition-Related Obligations

Acquisition-Related Obligations	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Acquisition-Related Obligations	Acquisition-Related Obligations Acquisition-related obligations consisted of the following: June 30, 2021 December 31, 2020 Contingent Revenue Obligation $ 23,904 $ 28,967 Environmental Settlement Obligations 9,702 10,391 UMWA Funds Settlement Liability 2,000 2,000 Discount (768) (1,491) Total acquisition-related obligations 34,838 39,867 Less current portion (22,866) (19,099) Acquisition-related obligations, net of current portion $ 11,972 $ 20,768 Contingent Revenue Obligation As of June 30, 2021 and December 31, 2020, the carrying value of the Contingent Revenue Obligation was $23,904 and $28,967, with $13,465 and $11,393 classified as current, respectively, classified as an acquisition-related obligation in the Condensed Consolidated Balance Sheets. Refer to Note 12 for further disclosures related to the fair value assignment and methods used. During the second quarter of 2021, the Company paid $11,396 pursuant to the terms of the Contingent Revenue Obligation.

Asset Retirement Obligations

Asset Retirement Obligations	6 Months Ended
	Jun. 30, 2021
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations	Asset Retirement Obligations The following table summarizes the changes in asset retirement obligations for the six months ended June 30, 2021: Total asset retirement obligations at December 31, 2020 $ 165,064 Accretion for the period 13,296 Revisions in estimated cash flows (17) Expenditures for the period (8,592) Total asset retirement obligations at June 30, 2021 169,751 Less current portion (1) (28,911) Long-term portion $ 140,840

Fair Value of Financial Instrum

Fair Value of Financial Instruments and Fair Value Measurements	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments and Fair Value Measurements	Fair Value of Financial Instruments and Fair Value Measurements The estimated fair values of financial instruments are determined based on relevant market information. These estimates involve uncertainty and cannot be determined with precision. The carrying amounts for cash and cash equivalents, trade accounts receivable, net, prepaid expenses and other current assets, short-term and long-term restricted cash, short-term and long-term deposits, trade accounts payable, and accrued expenses and other current liabilities approximate fair value as of June 30, 2021 and December 31, 2020 due to the short maturity of these instruments. The following tables set forth by level, within the fair value hierarchy, the Company’s long-term debt at fair value as of June 30, 2021 and December 31, 2020: June 30, 2021 Carrying Amount (1) Total Fair Value Quoted Prices in Active Markets Significant Other Observable Inputs Significant Unobservable Inputs Term Loan Credit Facility - due June 2024 $ 541,572 $ 488,626 $ — $ 488,626 $ — LCC Note Payable 26,046 25,172 — — 25,172 LCC Water Treatment Obligation 5,384 4,945 — — 4,945 Total long-term debt $ 573,002 $ 518,743 $ — $ 488,626 $ 30,117 December 31, 2020 Carrying Amount (1) Total Fair Value Quoted Prices in Active Markets Significant Other Observable Inputs Significant Unobservable Inputs Term Loan Credit Facility - due June 2024 $ 540,643 $ 379,614 $ — $ 379,614 $ — ABL Facility - due April 2022 3,350 3,057 — — 3,057 LCC Note Payable 24,423 20,328 — — 20,328 LCC Water Treatment Obligation 5,636 4,281 — — 4,281 Total long-term debt $ 574,052 $ 407,280 $ — $ 379,614 $ 27,666 (1) Net of debt discounts and debt issuance costs. The following tables set forth by level, within the fair value hierarchy, the Company’s acquisition-related obligations at fair value as of June 30, 2021 and December 31, 2020: June 30, 2021 Carrying Amount (1) Total Fair Value Quoted Prices in Active Markets Significant Other Observable Inputs Significant Unobservable Inputs UMWA Funds Settlement Liability $ 1,823 $ 1,797 $ — $ — $ 1,797 Environmental Settlement Obligations 9,111 8,764 — — 8,764 Total acquisition-related obligations $ 10,934 $ 10,561 $ — $ — $ 10,561 December 31, 2020 Carrying Amount (1) Total Fair Value Quoted Prices in Active Markets Significant Other Observable Inputs Significant Unobservable Inputs UMWA Funds Settlement Liability $ 1,662 $ 1,426 $ — $ — $ 1,426 Environmental Settlement Obligations 9,237 7,760 — — 7,760 Total acquisition-related obligations $ 10,899 $ 9,186 $ — $ — $ 9,186 (1) Net of discounts. The following table sets forth by level, within the fair value hierarchy, the Company’s financial and non-financial assets and liabilities that were accounted for at fair value on a recurring basis as of June 30, 2021 and December 31, 2020. Financial and non-financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement requires judgment, and may affect the determination of fair value for assets and liabilities and their placement within the fair value hierarchy levels. June 30, 2021 Total Fair Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Contingent Revenue Obligation $ 23,904 $ — $ — $ 23,904 Trading securities $ 31,189 $ 29,311 $ 1,878 $ — December 31, 2020 Total Fair Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Contingent Revenue Obligation $ 28,967 $ — $ — $ 28,967 Trading securities $ 22,498 $ 20,092 $ 2,406 $ — The following tables present a reconciliation of the financial and non-financial assets and liabilities that were accounted for at fair value on a recurring basis and that were categorized within Level 3 of the fair value hierarchy: December 31, 2020 Payments Loss (Gain) Recognized in Earnings (1) Transfer In (Out) of Level 3 Fair Value Hierarchy June 30, 2021 Contingent Revenue Obligation $ 28,967 $ (11,396) $ 6,333 $ — $ 23,904 (1) The loss recognized in earnings resulted primarily from a decrease in the annual risk-free interest rate as of June 30, 2021. December 31, 2019 Payments Loss (Gain) Recognized in Earnings (1) Transfer In (Out) of Level 3 Fair Value Hierarchy June 30, 2020 Contingent Revenue Obligation $ 52,427 $ (14,710) $ (17,049) $ — $ 20,668 (1) The gain recognized in earnings resulted primarily from a change in the forecasted future revenue associated with this obligation and an increase in annualized volatility as of June 30, 2020. The following methods and assumptions were used to estimate the fair values of the assets and liabilities in the tables above: Level 1 Fair Value Measurements Trading Securities - Includes money market funds and other cash equivalents. The fair value is based on observable market data. Level 2 Fair Value Measurements Term Loan Credit Facility - due June 2024 - The fair value is based on the average between bid and ask prices provided by a third-party. As the fair value is based on observable market inputs and due to limited trading volume in the Term Loan Credit Facility, the Company has classified the fair value within Level 2 of the fair value hierarchy. Trading Securities - Includes certificates of deposit, mutual funds, corporate debt securities and U.S. treasury and agency securities. The fair values of the Company’s trading securities are obtained from a third-party pricing service provider. The fair values provided by the pricing service provider are based on observable market inputs including credit spreads and broker-dealer quotes, among other inputs. The Company classifies the prices obtained from the pricing services within Level 2 of the fair value hierarchy because the underlying inputs are directly observable from active markets. However, the pricing models used entail a certain amount of subjectivity and therefore differing judgments in how the underlying inputs are modeled could result in different estimates of fair value. Level 3 Fair Value Measurements ABL Facility - due April 2022 - Observable transactions are not available to aid in determining the fair value of this item. Therefore, the fair value was derived by using the expected present value approach in which estimated cash flows are discounted using a risk-free interest rate adjusted for credit risk (discount rate of approximately 9% as of December 31, 2020). LCC Note Payable, LCC Water Treatment Obligation, UMWA Funds Settlement Liability and Environmental Settlement Obligations - Observable transactions are not available to aid in determining the fair value of these items. Therefore, the fair value was derived by using the expected present value approach in which estimated cash flows are discounted using a risk-free interest rate adjusted for credit risk (discount rates of approximately 22% and 34% as of June 30, 2021 and December 31, 2020, respectively). Contingent Revenue Obligation - The fair value of the contingent revenue obligation was estimated using a Black-Scholes pricing model and is marked to market at each reporting period with changes in value reflected in earnings. The inputs included in the Black-Scholes pricing model are the Company's forecasted future revenue, the stated royalty rate, the remaining periods in the obligation, annual risk-free interest rate based on the U.S. Constant Maturity Treasury Curve and annualized volatility. The annualized volatility was calculated by observing volatilities for comparable companies with adjustments for the Company's size and leverage. The range of significant unobservable inputs used to value the contingent revenue obligation as of June 30, 2021 and December 31, 2020, are set forth in the following table: June 30, 2021 December 31, 2020 Forecasted future revenue $1.1 - $1.2 billion $0.9 - $1.1 billion Stated royalty rate 1.0% - 1.5% 1.0% - 1.5% Annualized volatility 17.6% - 40.1% (29.0%) 19.4% - 52.1% (28.0%)

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes For the six months ended June 30, 2021, the Company recorded income tax expense of $3 on a loss from continuing operations before income taxes of $51,278. The income tax expense differs from the expected statutory amount primarily due to the increase in the valuation allowance and the impact of state income taxes, net of federal impact, partially offset by the permanent impact of percentage depletion deductions. As of June 30, 2021, the Company anticipates that no current federal income tax liability will be generated in 2021. For the six months ended June 30, 2020, the Company recorded income tax benefit of $2,155 on a loss from continuing operations before income taxes of $120,087. The income tax benefit differs from the expected statutory amount primarily due to the increase in valuation allowance, partially offset by the permanent impact of percentage depletion deductions, the impact of state income taxes, net of federal tax impact, and the recording of a discrete tax benefit related to the refundability of previously sequestered AMT Credits. During the six months ended June 30, 2021, the Company recorded an increase of $6,184 to its deferred tax asset valuation allowance. The increase in the valuation allowance results from an increase in deferred tax assets for which the Company is unable to support realization. The Company currently is relying primarily on the reversal of taxable temporary differences, along with consideration of taxable income via carryback to prior years and tax planning strategies, to support the realization of deferred tax assets. For each reporting period, the Company updates its assessment regarding the realizability of its deferred tax assets, including scheduling the reversal of its deferred tax assets and liabilities, to determine the amount of valuation allowance needed. Scheduling the reversal of deferred tax asset and liability balances requires judgment and estimation. The Company believes the deferred tax liabilities relied upon as future taxable income in its assessment will reverse in the same period and jurisdiction and are of the same character as the temporary differences giving rise to the deferred tax assets that will be realized. The valuation allowance recorded represents the portion of deferred tax assets for which the Company is unable to support realization through the methods described above.

Employee Benefit Plans

Employee Benefit Plans	6 Months Ended
	Jun. 30, 2021
Compensation Related Costs [Abstract]
Employee Benefit Plans	Employee Benefit Plans The components of net periodic (benefit) expense other than the service cost component for the employee benefit plan obligations below are included in the line item miscellaneous income (loss), net in the Condensed Consolidated Statements of Operations. Pension The following table details the components of the net periodic benefit for pension obligations: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Interest cost $ 3,362 $ 4,656 $ 6,784 $ 9,391 Expected return on plan assets (7,119) (6,748) (14,366) (13,560) Amortization of net actuarial loss 734 521 1,609 990 Settlement — 63 — 1,230 Net periodic benefit $ (3,023) $ (1,508) $ (5,973) $ (1,949) During the three months ended June 30, 2021, an annual census data actuarial revaluation of pension obligations was performed, which resulted in a decrease in the liability for pension obligations of approximately $8,838 with the offset to accumulated other comprehensive gain and a slight increase in net periodic benefit to be recognized subsequent to the revaluation date. As a result of the recent funding relief granted under the American Rescue Plan Act, estimated contributions requirements to the pension plans were reduced relative to the Company’s previous estimates. The Company contributed $3,701 to the pension plans during the six months ended June 30, 2021 and expects to contribute $7,664 in the remainder of 2021. Black Lung The following table details the components of the net periodic expense for black lung obligations: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Service cost $ 739 $ 492 $ 1,478 $ 980 Interest cost 607 775 1,214 1,597 Expected return on plan assets (14) (14) (28) (27) Amortization of net actuarial loss 522 286 1,044 501 Net periodic expense $ 1,854 $ 1,539 $ 3,708 $ 3,051 Defined Contribution and Profit-Sharing Plans

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2021
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions There were no material related party transactions for the six months ended June 30, 2021 or 2020.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies (a) General Estimated losses from loss contingencies are accrued by a charge to income when information available indicates that it is probable that an asset has been impaired or a liability has been incurred and the amount of the loss can be reasonably estimated. If a loss contingency is not probable or reasonably estimable, disclosure of the loss contingency is made in the Condensed Consolidated Financial Statements when it is at least reasonably possible that a loss may be incurred and that the loss could be material. (b) Commitments and Contingencies Commitments The Company leases coal mining and other equipment under long-term financing and operating leases with varying terms. In addition, the Company leases mineral interests and surface rights from landowners under various terms and royalty rates. Other Commitments As of June 30, 2021, the Company has obligations under certain coal transportation agreements that contain minimum quantities to be shipped during contract periods from 2021 through 2022 with estimated obligations based on remaining tons to be shipped totaling $32,940 in 2022. The Company also has obligations under certain coal purchase agreements that contain minimum quantities to be purchased in the remainder of 2021 totaling an estimated $33,477, which includes an estimated $3,230 related to contractually committed fixed priced tons from vendors with historical performance resulting in less than 20% of the committed tonnage being delivered. Contingencies Extensive regulation of the impacts of mining on the environment and of maintaining workplace safety has had, and is expected to continue to have, a significant effect on the Company’s costs of production and results of operations. Further regulations, legislation or litigation in these areas may also cause the Company’s sales or profitability to decline by increasing costs or by hindering the Company’s ability to continue mining at existing operations or to permit new operations. During the normal course of business, contract-related matters arise between the Company and its customers. When a loss related to such matters is considered probable and can reasonably be estimated, the Company records a liability. As of June 30, 2021, per terms of the Cumberland Back-to-Back Coal Supply Agreements, the Company is required to purchase and sell 1,226 and 2,615 tons of coal in the remainder of 2021 and 2022 totaling $47,803 and $101,990, respectively. For the three and six months ended June 30, 2021, the Company purchased and sold 760 and 1,460 tons, respectively, totaling $29,487 and $56,553, respectively, under the Cumberland Back-to-Back Coal Supply Agreements. Cumberland Back-to-Back Coal Supply Agreements are scheduled to be fully performed by December 31, 2022. Future Federal Income Tax Refunds As of June 30, 2021, the Company has recorded $64,160 of current federal income tax receivable and associated interest receivable of $5,385 related to a net operating loss (“NOL”) carryback claim. Because the federal government was a creditor in the Alpha Natural Resources, Inc. bankruptcy proceedings, it is possible that the federal government could withhold some or all of the tax refund attributable to the NOL carryback claim and assert a right to set off the tax refund and associated interest receivable against its prepetition bankruptcy claims. (c) Guarantees and Financial Instruments with Off-Balance Sheet Risk In the normal course of business, the Company is a party to certain guarantees and financial instruments with off-balance sheet risk, such as bank letters of credit, performance or surety bonds, and other guarantees and indemnities related to the obligations of affiliated entities which are not reflected in the Company’s Condensed Consolidated Balance Sheets. However, the underlying liabilities that they secure, such as asset retirement obligations, workers’ compensation liabilities, and royalty obligations, are reflected in the Company’s Condensed Consolidated Balance Sheets. The Company is required to provide financial assurance in order to perform the post-mining reclamation required by its mining permits, pay workers’ compensation claims under workers’ compensation laws in various states, pay federal black lung benefits, and perform certain other obligations. In order to provide the required financial assurance, the Company generally uses surety bonds for post-mining reclamation and workers’ compensation obligations. The Company can also use bank letters of credit to collateralize certain obligations. As of June 30, 2021, the Company had $128,752 letters of credit outstanding under the Amended and Restated Asset-Based Revolving Credit Agreement. Additionally, as of June 30, 2021, the Company had $613 letters of credit outstanding under the Credit and Security Agreement dated June 30, 2017, and related amendments, between ANR, Inc. and First Tennessee Bank National Association. On March 31, 2021, the Amended and Restated Letter of Credit Agreement dated November 9, 2018 between ANR, Inc. and Citibank, N.A. was terminated. As of June 30, 2021, the Company had outstanding surety bonds with a total face amount of $211,694 to secure various obligations and commitments, including $30 attributable to discontinued operations. To secure the Company’s reclamation-related obligations, the Company has $42,211 of collateral supporting these obligations as of June 30, 2021. The Company meets frequently with its surety providers and has discussions with certain providers regarding the extent of and the terms of their participation in the program. These discussions may cause the Company to shift surety bonds between providers or to alter the terms of their participation in our program. To the extent that surety bonds become unavailable or the Company’s surety bond providers require additional collateral, the Company would seek to secure its obligations with letters of credit, cash deposits or other suitable forms of collateral. The Company’s failure to maintain, or inability to acquire, surety bonds or to provide a suitable alternative would have a material adverse effect on its liquidity. These failures could result from a variety of factors including lack of availability, higher cost or unfavorable market terms of new surety bonds, and the exercise by third-party surety bond issuers of their right to refuse to renew the surety. Amounts included in restricted cash represent cash deposits primarily invested in interest bearing accounts that are restricted as to withdrawal as required by certain agreements entered into by the Company and provide collateral to secure the following obligations which have been written on the Company’s behalf: June 30, 2021 December 31, 2020 Workers' compensation and black lung obligations $ 63,096 $ 69,725 Reclamation-related obligations 6,989 8,445 Financial payments and other performance obligations 22,673 17,863 Contingent revenue obligation escrow 3,794 9,311 Total restricted cash 96,552 105,344 Less current portion (1) (3,794) (9,311) Restricted cash, net of current portion $ 92,758 $ 96,033 (1) Included within prepaid expenses and other current assets on the Company’s Condensed Consolidated Balance Sheets. Restricted investments consist of Federal Deposit Insurance Company (“FDIC”) insured certificates of deposit, mutual funds, and U.S. treasury bills that are restricted as to withdrawal as required by certain agreements entered into by the Company and provide collateral to secure the following obligations which have been written on the Company’s behalf: June 30, 2021 December 31, 2020 Workers' compensation obligations $ 210 $ 51 Reclamation-related obligations 29,195 22,233 Financial payments and other performance obligations 2,037 1,484 Total restricted investments (1), (2) $ 31,442 $ 23,768 (1) Included within other non-current assets on the Company’s Condensed Consolidated Balance Sheets. (2) As of June 30, 2021 and December 31, 2020, respectively, $31,189 and $22,498 are classified as trading securities and $253 and $1,270 are classified as held-to-maturity securities. Deposits represent cash deposits held at third parties as required by certain agreements entered into by the Company to provide cash collateral to secure the following obligations which have been written on the Company’s behalf: June 30, 2021 December 31, 2020 Workers' compensation and black lung obligations $ 35 $ — Reclamation-related obligations 6,027 25,633 Financial payments and other performance obligations 732 1,596 Other operating agreements 902 1,018 Total deposits (1) $ 7,696 $ 28,247 (1) Included within prepaid expenses and other current assets and other non-current assets on the Company’s Condensed Consolidated Balance Sheets. DCMWC Reauthorization Process In July 2019, the U.S. Department of Labor (Division of Coal Mine Workers’ Compensation or “DCMWC”) began implementing a new authorization process for all self-insured coal mine operators. As requested by the DCMWC, the Company filed an application and supporting documentation for reauthorization to self-insure certain of its black lung obligations in October 2019. As a result of this application, the DCMWC notified the Company in a letter dated February 21, 2020 that the Company was reauthorized to self-insure certain of its black lung obligations for a period of one-year from February 21, 2020. The DCMWC reauthorization is contingent, however, upon the Company’s providing collateral of $65,700 to secure certain of its black lung obligations. This proposed collateral requirement is an increase from the approximate $2,600 in collateral that the Company currently provides to secure these self-insured black lung obligations. The reauthorization process provided the Company with the right to appeal the security determination in writing within 30 days of the date of the notification, which appeal period the DCMWC agreed to extend to May 22, 2020. The Company exercised this right of appeal in connection with the substantial increase in the amount of required collateral. However, there has been no substantive activity under the appeal since its filing. In February 2021, the U.S. Department of Labor withdrew its Federal Register notice seeking comments on its bulletin describing its new method of calculating collateral requirements. The Department removed the bulletin from its website in May 2021. If the Company’s appeal is unsuccessful, the Company may be required to provide additional letters of credit to receive the self-insurance reauthorization from the DCMWC or alternatively insure these black lung obligations through a third party provider that would likely also require the Company to provide collateral. Either of these outcomes could potentially reduce the Company’s liquidity. (d) Legal Proceedings The Company is party to legal proceedings from time to time. These proceedings, as well as governmental examinations, could involve various business units and a variety of claims including, but not limited to, contract disputes, personal injury claims, property damage claims (including those resulting from blasting, trucking and flooding), environmental and safety issues, securities-related matters and employment matters. While some legal matters may specify the damages claimed by the plaintiffs, many seek an unquantified amount of damages. Even when the amount of damages claimed against the Company or its subsidiaries is stated, (i) the claimed amount may be exaggerated or unsupported; (ii) the claim may be based on a novel legal theory or involve a large number of parties; (iii) there may be uncertainty as to the likelihood of a class being certified or the ultimate size of the class; (iv) there may be uncertainty as to the outcome of pending appeals or motions; and/or (v) there may be significant factual issues to be resolved. As a result, if such legal matters arise in the future, the Company may be unable to estimate a range of possible loss for matters that have not yet progressed sufficiently through discovery and development of important factual information and legal issues. The Company records accruals based on an estimate of the ultimate outcome of these matters, but these estimates can be difficult to determine and involve significant judgment.

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2021
Segment Reporting [Abstract]
Segment Information	Segment Information The Company extracts, processes and markets met and thermal coal from deep and surface mines for sale to steel and coke producers, industrial customers, and electric utilities. The Company conducts mining operations only in the United States with mines in Central Appalachia (“CAPP”). The Company has one reportable segment: Met, which consists of five active mines and two preparation plants in Virginia, fourteen active mines and five preparation plants in West Virginia, as well as expenses associated with certain idled/closed mines. Prior to the first quarter of 2021, the Company had two reportable segments: CAPP - Met and CAPP - Thermal. As a result of the Company’s continued strategic focus on the production of metallurgical coal and the reduction of thermal mining operations, the Company re-evaluated its previous conclusions with respect to its segment reporting during the first quarter of 2021. To conform to the current period reportable segments presentation, the prior periods have been restated to reflect the change in reportable segments. In addition to the one reportable segment, the All Other category includes general corporate overhead and corporate assets and liabilities, the former CAPP - Thermal operations consisting of one active mine and one preparation plant in West Virginia, and the elimination of certain intercompany activity, as well as expenses associated with certain idled/closed mines. Reportable segment operating results are regularly reviewed by the Chief Operating Decision Maker (“CODM”), who is the Chief Executive Officer of the Company. Segment operating results and capital expenditures for the three months ended June 30, 2021 and 2020 were as follows: Three Months Ended June 30, 2021 Met All Other Consolidated Total revenues $ 377,937 $ 17,338 $ 395,275 Depreciation, depletion, and amortization $ 25,686 $ 1,618 $ 27,304 Amortization of acquired intangibles, net $ 2,635 $ (82) $ 2,553 Adjusted EBITDA $ 46,786 $ (6,869) $ 39,917 Capital expenditures $ 17,203 $ 441 $ 17,644 Three Months Ended June 30, 2020 Met All Other Consolidated Total revenues $ 316,534 $ 37,406 $ 353,940 Depreciation, depletion, and amortization $ 38,779 $ 8,290 $ 47,069 Amortization of acquired intangibles, net $ 2,759 $ (878) $ 1,881 Adjusted EBITDA $ 17,518 $ (10,373) $ 7,145 Capital expenditures $ 27,647 $ 3,011 $ 30,658 Segment operating results and capital expenditures for the six months ended June 30, 2021 and 2020 were as follows: Six Months Ended June 30, 2021 Met All Other Consolidated Total revenues $ 737,815 $ 43,713 $ 781,528 Depreciation, depletion, and amortization $ 52,222 $ 3,520 $ 55,742 Amortization of acquired intangibles, net $ 6,686 $ (264) $ 6,422 Adjusted EBITDA $ 79,368 $ (10,567) $ 68,801 Capital expenditures $ 37,526 $ 513 $ 38,039 Six Months Ended June 30, 2020 Met All Other Consolidated Total revenues $ 679,293 $ 77,451 $ 756,744 Depreciation, depletion, and amortization $ 80,501 $ 14,184 $ 94,685 Amortization of acquired intangibles, net $ 5,340 $ (2,948) $ 2,392 Adjusted EBITDA $ 86,636 $ (22,994) $ 63,642 Capital expenditures $ 60,781 $ 6,140 $ 66,921 The following tables present a reconciliation of net loss to Adjusted EBITDA for the three months ended June 30, 2021 and 2020: Three Months Ended June 30, 2021 Met All Other Consolidated Net loss from continuing operations $ 15,042 $ (33,632) $ (18,590) Interest expense 40 17,922 17,962 Interest income — (104) (104) Income tax expense — 8 8 Depreciation, depletion and amortization 25,686 1,618 27,304 Non-cash stock compensation expense 6 973 979 Mark-to-market adjustment - acquisition-related obligations — 3,157 3,157 Accretion on asset retirement obligations 3,377 3,271 6,648 Amortization of acquired intangibles, net 2,635 (82) 2,553 Adjusted EBITDA $ 46,786 $ (6,869) $ 39,917 Three Months Ended June 30, 2020 Met All Other Consolidated Net loss from continuing operations $ (27,097) $ (54,649) $ (81,746) Interest expense (377) 19,693 19,316 Interest income (3) (5,527) (5,530) Income tax expense — 33 33 Depreciation, depletion and amortization 38,779 8,290 47,069 Non-cash stock compensation expense (94) 1,138 1,044 Mark-to-market adjustment - acquisition-related obligations — (2,052) (2,052) Accretion on asset retirement obligations 3,551 3,018 6,569 Asset impairment and restructuring (1) — 20,498 20,498 Loss on partial settlement of benefit obligations — 63 63 Amortization of acquired intangibles, net 2,759 (878) 1,881 Adjusted EBITDA $ 17,518 $ (10,373) $ 7,145 (1) Refer to Note 8 for additional information on asset impairment and restructuring during the period. The following tables present a reconciliation of net loss to Adjusted EBITDA for the six months ended June 30, 2021 and 2020: Six Months Ended June 30, 2021 Met All Other Consolidated Net loss from continuing operations $ 13,604 $ (64,885) $ (51,281) Interest expense 83 35,869 35,952 Interest income (5) (263) (268) Income tax expense — 3 3 Depreciation, depletion and amortization 52,222 3,520 55,742 Non-cash stock compensation expense 16 3,147 3,163 Mark-to-market adjustment - acquisition-related obligations — 6,333 6,333 Accretion on asset retirement obligations 6,762 6,534 13,296 Asset impairment and restructuring (1) — (561) (561) Amortization of acquired intangibles, net 6,686 (264) 6,422 Adjusted EBITDA $ 79,368 $ (10,567) $ 68,801 (1) Refer to Note 8 for additional information on asset impairment and restructuring during the period. Six Months Ended June 30, 2020 Met All Other Consolidated Net loss from continuing operations $ (38,682) $ (79,250) $ (117,932) Interest expense (1,306) 38,798 37,492 Interest income (61) (6,437) (6,498) Income tax benefit — (2,155) (2,155) Depreciation, depletion and amortization 80,501 14,184 94,685 Non-cash stock compensation expense 305 2,817 3,122 Mark-to-market adjustment - acquisition-related obligations — (17,049) (17,049) Accretion on asset retirement obligations 7,087 6,121 13,208 Asset impairment and restructuring (1) 32,951 21,256 54,207 Management restructuring costs (2) 501 439 940 Loss on partial settlement of benefit obligations — 1,230 1,230 Amortization of acquired intangibles, net 5,340 (2,948) 2,392 Adjusted EBITDA $ 86,636 $ (22,994) $ 63,642 (1) Refer to Note 8 for additional information on asset impairment and restructuring during the period. (2) Management restructuring costs are related to severance expense associated with senior management changes in the three months ended March 31, 2020. No asset information has been disclosed as the CODM does not regularly review asset information by reportable segment. The Company markets produced, processed and purchased coal to customers in the United States and in international markets, primarily India, Brazil, and Turkey. Revenue is tracked within the Company’s accounting records based on the product destination. Export coal revenues were the following: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Total coal revenues $ 393,458 $ 353,115 $ 778,910 $ 754,575 Export coal revenues $ 256,017 $ 240,662 $ 499,800 $ 492,116 Export coal revenues as % of total coal revenues 65 % 68 % 64 % 65 % Countries with export coal revenue exceeding 10% of total revenue India India, Turkey, Brazil India, Brazil India, Brazil

Business and Basis of Present_2

Business and Basis of Presentation (Policies)	6 Months Ended
	Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation Together, the condensed consolidated statements of operations, comprehensive loss, balance sheets, cash flows and stockholders’ equity for the Company are referred to as the “Condensed Consolidated Financial Statements.” The Condensed Consolidated Financial Statements are also referenced across periods as “Condensed Consolidated Statements of Operations,” “Condensed Consolidated Statements of Comprehensive Loss,” “Condensed Consolidated Balance Sheets,” “Condensed Consolidated Statements of Cash Flows,” and “Condensed Consolidated Statements of Stockholders’ Equity.” The Company’s former Northern Appalachia (“NAPP”) operations results of operations and financial position are reported as discontinued operations in the Condensed Consolidated Financial Statements. The historical information in the accompanying Notes to the Condensed Consolidated Financial Statements has been restated to reflect the effects of the Company’s former NAPP operations being reported as discontinued operations in the Condensed Consolidated Financial Statements. Refer to Note 2 for further information on discontinued operations. The Condensed Consolidated Financial Statements include all wholly-owned subsidiaries’ results of operations for the three and six months ended June 30, 2021 and 2020. All significant intercompany transactions have been eliminated in consolidation.
Liquidity Risk and Uncertainties	Liquidity Risks and UncertaintiesThe Company believes it will have sufficient liquidity to meet its working capital requirements, anticipated capital expenditures, debt service requirements, acquisition-related obligations, and reclamation obligations for the 12 months subsequent to the issuance of these financial statements. However, the Company may need to raise additional funds if market conditions deteriorate and may not be able to do so in a timely fashion, or at all. The Company relies on a number of assumptions in budgeting for future activities. These include the costs for mine development to sustain capacity of its operating mines, cash flows from operations, effects of regulation and taxes by governmental agencies, mining technology improvements and reclamation costs. These assumptions are inherently subject to significant business, political, economic, regulatory, environmental and competitive uncertainties, contingencies and risks, all of which are difficult to predict and many of which are beyond the Company’s control. Therefore, the Company’s cash on hand and from future operations will be subject to any significant changes in these assumptions.
Recently Adopted Accounting Guidance	Recently Adopted Accounting Guidance Convertible Debt and Contracts in Entity’s Own Equity : In August 2020, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40) (“ASU 2020-06”). The amendments in this update simplify the accounting for certain financial instruments with characteristics of liabilities and equity, including convertible instruments and contracts in an entity’s own equity, such as the Company’s outstanding Series A warrants. For public business entities, the standard is effective for fiscal years beginning after December 15, 2021, with early adoption permitted. The Company adopted ASU 2020-06 during the first quarter of 2021. The adoption of this ASU did not have a material impact on the Company's Condensed Consolidated Financial Statements and related disclosures. Reference Rate Reform : In January 2021, the FASB issued ASU 2021-01, Reference Rate Reform (Topic 848) (“ASU 2021-01”). The amendments in this update clarify that certain optional expedients and exceptions in Topic 848 for contract modifications and hedge accounting apply to derivatives that are affected by the discounting transition. For all entities, the standard is effective immediately. The Company adopted ASU 2021-01 during the first quarter of 2021. The adoption of this ASU did not have a material impact on the Company's Condensed Consolidated Financial Statements and related disclosures. Certain Modifications or Exchanges of Freestanding Equity-Classified Written Call Options: In May 2021, the FASB issued ASU 2021-04, Earnings Per Share (Topic 260), Debt—Modifications and Extinguishments (Subtopic 470-50), Compensation—Stock Compensation (Topic 718), and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40)

Discontinued Operations (Tables

Discontinued Operations (Tables)	6 Months Ended
	Jun. 30, 2021
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations	The major components of loss from discontinued operations before income taxes in the Condensed Consolidated Statements of Operations for the three and six months ended June 30, 2020 are as follows: Three Months Ended June 30, 2020 (1) Six Months Ended June 30, 2020 (1) Revenues: Total revenues $ 57,898 $ 125,554 Costs and expenses: Cost of coal sales (exclusive of items shown separately below) 47,843 110,265 Depreciation, depletion and amortization 2,193 9,042 Accretion on asset retirement obligations 735 1,471 Selling, general and administrative expenses (2) 169 1,387 Asset impairment and restructuring (3) 163,675 163,675 Other non-major income items, net (162) (109) Loss from discontinued operations before income taxes $ (156,555) $ (160,177) (1) Includes minor residual activity related to the Company’s former Powder River Basin (“PRB”) operations. (2) Represents professional and legal fees. (3) Refer to Note 8 for additional information on asset impairment and restructuring during the periods. The major components of assets and liabilities that are classified as discontinued operations in the Condensed Consolidated Balance Sheets are as follows: June 30, 2021 December 31, 2020 Assets: Trade accounts receivable, net of allowance for doubtful accounts $ — $ 7,504 Prepaid expenses and other current assets $ 2,157 $ 3,431 Other non-current assets (1) $ 9,477 $ 9,473 Liabilities: Trade accounts payable, accrued expenses and other current liabilities $ 7,101 $ 12,306 Workers’ compensation and black lung obligations, non-current $ 26,205 $ 27,799 Other non-current liabilities $ 1,291 $ 1,291 (1) Primarily comprised of workers’ compensation insurance receivable and long-term restricted investments collateralizing workers’ compensation obligations. The major components of cash flows related to discontinued operations are as follows: Six Months Ended June 30, 2020 Depreciation, depletion and amortization $ 9,042 Capital expenditures $ 24,169 Other significant operating non-cash items related to discontinued operations: Accretion on asset retirement obligations $ 1,471 Asset impairment and restructuring $ 163,675

Revenue (Tables)

Revenue (Tables)	6 Months Ended
	Jun. 30, 2021
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following tables disaggregate the Company’s coal revenues by product category and by market to depict how the nature, amount, timing, and uncertainty of the Company’s coal revenues and cash flows are affected by economic factors: Three Months Ended June 30, 2021 Met Coal Thermal Coal Total Export coal revenues $ 250,324 $ 5,693 $ 256,017 Domestic coal revenues 105,235 32,206 137,441 Total coal revenues $ 355,559 $ 37,899 $ 393,458 Three Months Ended June 30, 2020 Met Coal Thermal Coal Total Export coal revenues $ 230,293 $ 10,369 $ 240,662 Domestic coal revenues 82,903 29,550 112,453 Total coal revenues $ 313,196 $ 39,919 $ 353,115 Six Months Ended June 30, 2021 Met Thermal Total Export coal revenues $ 493,076 $ 6,724 $ 499,800 Domestic coal revenues 205,477 73,633 279,110 Total coal revenues $ 698,553 $ 80,357 $ 778,910 Six Months Ended June 30, 2020 Met Thermal Total Export coal revenues $ 474,364 $ 17,752 $ 492,116 Domestic coal revenues 197,591 64,868 262,459 Total coal revenues $ 671,955 $ 82,620 $ 754,575
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction	The following table includes estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied as of June 30, 2021: Remainder of 2021 2022 2023 2024 2025 Total Estimated coal revenues $ 65,852 $ 50,935 $ — $ — $ — $ 116,787

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss (Tables)	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following tables summarize the changes to accumulated other comprehensive loss during the six months ended June 30, 2021 and 2020: Balance January 1, 2021 Other comprehensive income before reclassifications Amounts reclassified from accumulated other comprehensive loss Balance June 30, 2021 Employee benefit costs $ (111,985) $ 8,838 $ 2,826 $ (100,321) Balance January 1, 2020 Other comprehensive loss before reclassifications Amounts reclassified from accumulated other comprehensive loss Balance June 30, 2020 Employee benefit costs $ (58,616) $ (14,154) $ 3,023 $ (69,747) The following table summarizes the amounts reclassified from accumulated other comprehensive loss and the Condensed Consolidated Statements of Operations line items affected by the reclassification during the three and six months ended June 30, 2021 and 2020: Details about accumulated other comprehensive loss components Amounts reclassified from accumulated other comprehensive loss Affected line item in the Condensed Consolidated Statements of Operations Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Employee benefit costs: Amortization of net actuarial loss (1) $ 1,342 $ 934 $ 2,826 $ 1,728 Miscellaneous income (loss), net Settlement (1) — 95 — 1,295 Miscellaneous income (loss), net Total before income tax $ 1,342 $ 1,029 $ 2,826 $ 3,023 Income tax — — — — Income tax (expense) benefit Total, net of income tax $ 1,342 $ 1,029 $ 2,826 $ 3,023 (1) These accumulated other comprehensive loss components are included in the computation of net periodic benefit costs for certain employee benefit plans. Refer to Note 14.

Inventories, net (Tables)

Inventories, net (Tables)	6 Months Ended
	Jun. 30, 2021
Inventory Disclosure [Abstract]
Schedule of Inventory	Inventories, net consisted of the following: June 30, 2021 December 31, 2020 Raw coal $ 21,071 $ 15,084 Saleable coal 96,768 69,262 Materials, supplies and other, net 26,577 23,705 Total inventories, net $ 144,416 $ 108,051

Acquired Intangibles (Tables)

Acquired Intangibles (Tables)	6 Months Ended
	Jun. 30, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangibles	The balances and respective balance sheet classifications of such assets and liabilities as of June 30, 2021 and December 31, 2020, net of accumulated amortization, are set forth in the following tables: June 30, 2021 Assets (1) Liabilities (2) Net Total Coal supply agreements, net $ — $ (163) $ (163) Acquired mine permits, net 81,610 — 81,610 Total $ 81,610 $ (163) $ 81,447 December 31, 2020 Assets (1) Liabilities (2) Net Total Coal supply agreements, net $ — $ (327) $ (327) Acquired mine permits, net 88,196 — 88,196 Total $ 88,196 $ (327) $ 87,869 (1) Included within other acquired intangibles, net of accumulated amortization on the Company’s Condensed Consolidated Balance Sheets. (2) Included within other non-current liabilities on the Company’s Condensed Consolidated Balance Sheets. The following table details the amortization of the Company’s acquired intangibles included within amortization of acquired intangibles, net in the Condensed Consolidated Statements of Operations: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Amortization of mine permits $ 2,635 $ 3,320 $ 6,586 $ 6,648 Amortization of above-market coal supply agreements $ — $ — $ — $ 18 Amortization of below-market coal supply agreements (82) (1,439) (164) (4,274) Net income $ (82) $ (1,439) $ (164) $ (4,256)

Asset Impairment and Restruct_2

Asset Impairment and Restructuring (Tables)	6 Months Ended
	Jun. 30, 2021
Restructuring and Related Activities [Abstract]
Details of Impairment of Long-Lived Assets Held and Used by Asset	The following tables present the details of the long-lived asset impairment during the three and six months ended June 30, 2020: Three Months Ended June 30, 2020 Six Months Ended June 30, 2020 Continuing operations: Met $ — $ 32,951 All Other 17,390 18,148 Total from continuing operations $ 17,390 $ 51,099 Discontinued operations: $ 144,348 $ 144,348 Total long-lived asset impairment: $ 161,738 $ 195,447 Three Months Ended June 30, 2020 Six Months Ended June 30, 2020 Continuing operations: Mineral rights, net $ 2,241 $ 24,066 Property, plant, and equipment, net 6,496 12,562 Acquired mine permits, net 8,653 14,471 Total from continuing operations $ 17,390 $ 51,099 Discontinued operations: Mineral rights, net $ 16,364 $ 16,364 Property, plant, and equipment, net 127,984 127,984 Total from discontinued operations $ 144,348 $ 144,348 Total long-lived asset impairment: Mineral rights, net $ 18,605 $ 40,430 Property, plant, and equipment, net 134,480 140,546 Acquired mine permits, net 8,653 14,471 Total long-lived asset impairment $ 161,738 $ 195,447
Schedule of Restructuring Expense	As a result of the strategic actions discussed above, the Company recorded restructuring expense during the three and six months ended June 30, 2020 as follows: Three and Six Months Ended June 30, 2020 Total Restructuring Continuing Operations (3) Discontinued Operations Severance and employee-related benefits (1) $ 20,553 $ 2,301 $ 18,252 Other costs (2) 1,882 807 1,075 Total restructuring expense $ 22,435 $ 3,108 $ 19,327 (1) Severance and employee-related benefits were considered probable and estimable based on provisions of contractual agreements and existing employee benefit plans. (2) Includes accelerated amortization of deferred longwall move expenses of $668, allowance for advanced mining royalties of $407, and allowance for obsolete materials and supplies inventory of $807.

Long-Term Debt (Tables)

Long-Term Debt (Tables)	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Schedule of Long-term Debt Instruments	Long-term debt consisted of the following: June 30, 2021 December 31, 2020 Term Loan Credit Facility - due June 2024 $ 550,564 $ 553,373 ABL Facility - due April 2022 — 3,350 LCC Note Payable 27,500 27,500 LCC Water Treatment Obligation 6,250 6,875 Other (1) 6,665 8,475 Debt discount and issuance costs (11,312) (17,046) Total long-term debt 579,667 582,527 Less current portion (29,404) (28,830) Long-term debt, net of current portion $ 550,263 $ 553,697 (1) Includes financing leases.

Acquisition-Related Obligatio_2

Acquisition-Related Obligations (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Schedule of Acquisition-Related Obligations	Acquisition-related obligations consisted of the following: June 30, 2021 December 31, 2020 Contingent Revenue Obligation $ 23,904 $ 28,967 Environmental Settlement Obligations 9,702 10,391 UMWA Funds Settlement Liability 2,000 2,000 Discount (768) (1,491) Total acquisition-related obligations 34,838 39,867 Less current portion (22,866) (19,099) Acquisition-related obligations, net of current portion $ 11,972 $ 20,768

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	6 Months Ended
	Jun. 30, 2021
Asset Retirement Obligation Disclosure [Abstract]
Summary of Changes in Asset Retirement Obligations	The following table summarizes the changes in asset retirement obligations for the six months ended June 30, 2021: Total asset retirement obligations at December 31, 2020 $ 165,064 Accretion for the period 13,296 Revisions in estimated cash flows (17) Expenditures for the period (8,592) Total asset retirement obligations at June 30, 2021 169,751 Less current portion (1) (28,911) Long-term portion $ 140,840

Fair Value of Financial Instr_2

Fair Value of Financial Instruments and Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements, Nonrecurring	The following tables set forth by level, within the fair value hierarchy, the Company’s long-term debt at fair value as of June 30, 2021 and December 31, 2020: June 30, 2021 Carrying Amount (1) Total Fair Value Quoted Prices in Active Markets Significant Other Observable Inputs Significant Unobservable Inputs Term Loan Credit Facility - due June 2024 $ 541,572 $ 488,626 $ — $ 488,626 $ — LCC Note Payable 26,046 25,172 — — 25,172 LCC Water Treatment Obligation 5,384 4,945 — — 4,945 Total long-term debt $ 573,002 $ 518,743 $ — $ 488,626 $ 30,117 December 31, 2020 Carrying Amount (1) Total Fair Value Quoted Prices in Active Markets Significant Other Observable Inputs Significant Unobservable Inputs Term Loan Credit Facility - due June 2024 $ 540,643 $ 379,614 $ — $ 379,614 $ — ABL Facility - due April 2022 3,350 3,057 — — 3,057 LCC Note Payable 24,423 20,328 — — 20,328 LCC Water Treatment Obligation 5,636 4,281 — — 4,281 Total long-term debt $ 574,052 $ 407,280 $ — $ 379,614 $ 27,666 (1) Net of debt discounts and debt issuance costs. The following tables set forth by level, within the fair value hierarchy, the Company’s acquisition-related obligations at fair value as of June 30, 2021 and December 31, 2020: June 30, 2021 Carrying Amount (1) Total Fair Value Quoted Prices in Active Markets Significant Other Observable Inputs Significant Unobservable Inputs UMWA Funds Settlement Liability $ 1,823 $ 1,797 $ — $ — $ 1,797 Environmental Settlement Obligations 9,111 8,764 — — 8,764 Total acquisition-related obligations $ 10,934 $ 10,561 $ — $ — $ 10,561 December 31, 2020 Carrying Amount (1) Total Fair Value Quoted Prices in Active Markets Significant Other Observable Inputs Significant Unobservable Inputs UMWA Funds Settlement Liability $ 1,662 $ 1,426 $ — $ — $ 1,426 Environmental Settlement Obligations 9,237 7,760 — — 7,760 Total acquisition-related obligations $ 10,899 $ 9,186 $ — $ — $ 9,186 (1) Net of discounts.
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following table sets forth by level, within the fair value hierarchy, the Company’s financial and non-financial assets and liabilities that were accounted for at fair value on a recurring basis as of June 30, 2021 and December 31, 2020. Financial and non-financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement requires judgment, and may affect the determination of fair value for assets and liabilities and their placement within the fair value hierarchy levels. June 30, 2021 Total Fair Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Contingent Revenue Obligation $ 23,904 $ — $ — $ 23,904 Trading securities $ 31,189 $ 29,311 $ 1,878 $ — December 31, 2020 Total Fair Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Contingent Revenue Obligation $ 28,967 $ — $ — $ 28,967 Trading securities $ 22,498 $ 20,092 $ 2,406 $ — The following tables present a reconciliation of the financial and non-financial assets and liabilities that were accounted for at fair value on a recurring basis and that were categorized within Level 3 of the fair value hierarchy: December 31, 2020 Payments Loss (Gain) Recognized in Earnings (1) Transfer In (Out) of Level 3 Fair Value Hierarchy June 30, 2021 Contingent Revenue Obligation $ 28,967 $ (11,396) $ 6,333 $ — $ 23,904 (1) The loss recognized in earnings resulted primarily from a decrease in the annual risk-free interest rate as of June 30, 2021. December 31, 2019 Payments Loss (Gain) Recognized in Earnings (1) Transfer In (Out) of Level 3 Fair Value Hierarchy June 30, 2020 Contingent Revenue Obligation $ 52,427 $ (14,710) $ (17,049) $ — $ 20,668 June 30, 2021 December 31, 2020 Forecasted future revenue $1.1 - $1.2 billion $0.9 - $1.1 billion Stated royalty rate 1.0% - 1.5% 1.0% - 1.5% Annualized volatility 17.6% - 40.1% (29.0%) 19.4% - 52.1% (28.0%)

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	6 Months Ended
	Jun. 30, 2021
Compensation Related Costs [Abstract]
Schedule of Net Periodic Benefit Cost	The following table details the components of the net periodic benefit for pension obligations: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Interest cost $ 3,362 $ 4,656 $ 6,784 $ 9,391 Expected return on plan assets (7,119) (6,748) (14,366) (13,560) Amortization of net actuarial loss 734 521 1,609 990 Settlement — 63 — 1,230 Net periodic benefit $ (3,023) $ (1,508) $ (5,973) $ (1,949) The following table details the components of the net periodic expense for black lung obligations: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Service cost $ 739 $ 492 $ 1,478 $ 980 Interest cost 607 775 1,214 1,597 Expected return on plan assets (14) (14) (28) (27) Amortization of net actuarial loss 522 286 1,044 501 Net periodic expense $ 1,854 $ 1,539 $ 3,708 $ 3,051

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Schedule of Restricted Cash Deposits	Amounts included in restricted cash represent cash deposits primarily invested in interest bearing accounts that are restricted as to withdrawal as required by certain agreements entered into by the Company and provide collateral to secure the following obligations which have been written on the Company’s behalf: June 30, 2021 December 31, 2020 Workers' compensation and black lung obligations $ 63,096 $ 69,725 Reclamation-related obligations 6,989 8,445 Financial payments and other performance obligations 22,673 17,863 Contingent revenue obligation escrow 3,794 9,311 Total restricted cash 96,552 105,344 Less current portion (1) (3,794) (9,311) Restricted cash, net of current portion $ 92,758 $ 96,033 (1) Included within prepaid expenses and other current assets on the Company’s Condensed Consolidated Balance Sheets.
Schedule of Restricted Investments and Deposit Assets	Restricted investments consist of Federal Deposit Insurance Company (“FDIC”) insured certificates of deposit, mutual funds, and U.S. treasury bills that are restricted as to withdrawal as required by certain agreements entered into by the Company and provide collateral to secure the following obligations which have been written on the Company’s behalf: June 30, 2021 December 31, 2020 Workers' compensation obligations $ 210 $ 51 Reclamation-related obligations 29,195 22,233 Financial payments and other performance obligations 2,037 1,484 Total restricted investments (1), (2) $ 31,442 $ 23,768 (1) Included within other non-current assets on the Company’s Condensed Consolidated Balance Sheets. (2) As of June 30, 2021 and December 31, 2020, respectively, $31,189 and $22,498 are classified as trading securities and $253 and $1,270 are classified as held-to-maturity securities. Deposits represent cash deposits held at third parties as required by certain agreements entered into by the Company to provide cash collateral to secure the following obligations which have been written on the Company’s behalf: June 30, 2021 December 31, 2020 Workers' compensation and black lung obligations $ 35 $ — Reclamation-related obligations 6,027 25,633 Financial payments and other performance obligations 732 1,596 Other operating agreements 902 1,018 Total deposits (1) $ 7,696 $ 28,247 (1) Included within prepaid expenses and other current assets and other non-current assets on the Company’s Condensed Consolidated Balance Sheets.

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2021
Segment Reporting [Abstract]
Schedule of Segment Operating Results and Capital Expenditures	Segment operating results and capital expenditures for the three months ended June 30, 2021 and 2020 were as follows: Three Months Ended June 30, 2021 Met All Other Consolidated Total revenues $ 377,937 $ 17,338 $ 395,275 Depreciation, depletion, and amortization $ 25,686 $ 1,618 $ 27,304 Amortization of acquired intangibles, net $ 2,635 $ (82) $ 2,553 Adjusted EBITDA $ 46,786 $ (6,869) $ 39,917 Capital expenditures $ 17,203 $ 441 $ 17,644 Three Months Ended June 30, 2020 Met All Other Consolidated Total revenues $ 316,534 $ 37,406 $ 353,940 Depreciation, depletion, and amortization $ 38,779 $ 8,290 $ 47,069 Amortization of acquired intangibles, net $ 2,759 $ (878) $ 1,881 Adjusted EBITDA $ 17,518 $ (10,373) $ 7,145 Capital expenditures $ 27,647 $ 3,011 $ 30,658 Segment operating results and capital expenditures for the six months ended June 30, 2021 and 2020 were as follows: Six Months Ended June 30, 2021 Met All Other Consolidated Total revenues $ 737,815 $ 43,713 $ 781,528 Depreciation, depletion, and amortization $ 52,222 $ 3,520 $ 55,742 Amortization of acquired intangibles, net $ 6,686 $ (264) $ 6,422 Adjusted EBITDA $ 79,368 $ (10,567) $ 68,801 Capital expenditures $ 37,526 $ 513 $ 38,039 Six Months Ended June 30, 2020 Met All Other Consolidated Total revenues $ 679,293 $ 77,451 $ 756,744 Depreciation, depletion, and amortization $ 80,501 $ 14,184 $ 94,685 Amortization of acquired intangibles, net $ 5,340 $ (2,948) $ 2,392 Adjusted EBITDA $ 86,636 $ (22,994) $ 63,642 Capital expenditures $ 60,781 $ 6,140 $ 66,921 Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Total coal revenues $ 393,458 $ 353,115 $ 778,910 $ 754,575 Export coal revenues $ 256,017 $ 240,662 $ 499,800 $ 492,116 Export coal revenues as % of total coal revenues 65 % 68 % 64 % 65 % Countries with export coal revenue exceeding 10% of total revenue India India, Turkey, Brazil India, Brazil India, Brazil
Reconciliation of Net Income (Loss) to Adjusted EBITDA	The following tables present a reconciliation of net loss to Adjusted EBITDA for the three months ended June 30, 2021 and 2020: Three Months Ended June 30, 2021 Met All Other Consolidated Net loss from continuing operations $ 15,042 $ (33,632) $ (18,590) Interest expense 40 17,922 17,962 Interest income — (104) (104) Income tax expense — 8 8 Depreciation, depletion and amortization 25,686 1,618 27,304 Non-cash stock compensation expense 6 973 979 Mark-to-market adjustment - acquisition-related obligations — 3,157 3,157 Accretion on asset retirement obligations 3,377 3,271 6,648 Amortization of acquired intangibles, net 2,635 (82) 2,553 Adjusted EBITDA $ 46,786 $ (6,869) $ 39,917 Three Months Ended June 30, 2020 Met All Other Consolidated Net loss from continuing operations $ (27,097) $ (54,649) $ (81,746) Interest expense (377) 19,693 19,316 Interest income (3) (5,527) (5,530) Income tax expense — 33 33 Depreciation, depletion and amortization 38,779 8,290 47,069 Non-cash stock compensation expense (94) 1,138 1,044 Mark-to-market adjustment - acquisition-related obligations — (2,052) (2,052) Accretion on asset retirement obligations 3,551 3,018 6,569 Asset impairment and restructuring (1) — 20,498 20,498 Loss on partial settlement of benefit obligations — 63 63 Amortization of acquired intangibles, net 2,759 (878) 1,881 Adjusted EBITDA $ 17,518 $ (10,373) $ 7,145 (1) Refer to Note 8 for additional information on asset impairment and restructuring during the period. The following tables present a reconciliation of net loss to Adjusted EBITDA for the six months ended June 30, 2021 and 2020: Six Months Ended June 30, 2021 Met All Other Consolidated Net loss from continuing operations $ 13,604 $ (64,885) $ (51,281) Interest expense 83 35,869 35,952 Interest income (5) (263) (268) Income tax expense — 3 3 Depreciation, depletion and amortization 52,222 3,520 55,742 Non-cash stock compensation expense 16 3,147 3,163 Mark-to-market adjustment - acquisition-related obligations — 6,333 6,333 Accretion on asset retirement obligations 6,762 6,534 13,296 Asset impairment and restructuring (1) — (561) (561) Amortization of acquired intangibles, net 6,686 (264) 6,422 Adjusted EBITDA $ 79,368 $ (10,567) $ 68,801 (1) Refer to Note 8 for additional information on asset impairment and restructuring during the period. Six Months Ended June 30, 2020 Met All Other Consolidated Net loss from continuing operations $ (38,682) $ (79,250) $ (117,932) Interest expense (1,306) 38,798 37,492 Interest income (61) (6,437) (6,498) Income tax benefit — (2,155) (2,155) Depreciation, depletion and amortization 80,501 14,184 94,685 Non-cash stock compensation expense 305 2,817 3,122 Mark-to-market adjustment - acquisition-related obligations — (17,049) (17,049) Accretion on asset retirement obligations 7,087 6,121 13,208 Asset impairment and restructuring (1) 32,951 21,256 54,207 Management restructuring costs (2) 501 439 940 Loss on partial settlement of benefit obligations — 1,230 1,230 Amortization of acquired intangibles, net 5,340 (2,948) 2,392 Adjusted EBITDA $ 86,636 $ (22,994) $ 63,642 (1) Refer to Note 8 for additional information on asset impairment and restructuring during the period. (2) Management restructuring costs are related to severance expense associated with senior management changes in the three months ended March 31, 2020.

Discontinued Operations - Narra

Discontinued Operations - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Guarantor Obligations [Line Items]
Loss from discontinued operations before income taxes	$ (401)	$ (156,555)	$ (638)	$ (160,177)
Discontinued Operations, Disposed of by Sale | Cumberland Transaction
Guarantor Obligations [Line Items]
Remaining surety bond and expected to be released in short-term	$ 30		$ 30

Discontinued Operations - Major

Discontinued Operations - Major Components of Net Income (Loss) (Details) - Cumberland and PRB Transaction - Discontinued Operations - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Revenues:
Total revenues	$ 57,898	$ 125,554
Costs and expenses:
Cost of coal sales (exclusive of items shown separately below)	47,843	110,265
Depreciation, depletion and amortization	2,193	9,042
Accretion on asset retirement obligations	735	1,471
Selling, general and administrative expenses	169	1,387
Asset impairment and restructuring	163,675	163,675
Other non-major income items, net	(162)	(109)
Loss from discontinued operations before income taxes	$ (156,555)	$ (160,177)

Discontinued Operations - Maj_2

Discontinued Operations - Major Components of Asset and Liabilities (Details) - Cumberland and PRB Transaction - Discontinued Operations - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets:
Trade accounts receivable, net of allowance for doubtful accounts	$ 0	$ 7,504
Prepaid expenses and other current assets	2,157	3,431
Other non-current assets	9,477	9,473
Liabilities:
Trade accounts payable, accrued expenses and other current liabilities	7,101	12,306
Workers’ compensation and black lung obligations, non-current	26,205	27,799
Other non-current liabilities	$ 1,291	$ 1,291

Discontinued Operations - Maj_3

Discontinued Operations - Major Components of Cash Flows (Details) - Cumberland and PRB Transaction - Discontinued Operations - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation, depletion and amortization		$ 9,042
Capital expenditures		24,169
Accretion on asset retirement obligations	$ 735	1,471
Asset impairment and restructuring		$ 163,675

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues	$ 393,458	$ 353,115	$ 778,910	$ 754,575
Coal
Disaggregation of Revenue [Line Items]
Revenues	393,458	353,115	778,910	754,575
Met Coal
Disaggregation of Revenue [Line Items]
Revenues	355,559	313,196	698,553	671,955
Thermal Coal
Disaggregation of Revenue [Line Items]
Revenues	37,899	39,919	80,357	82,620
Export coal revenues
Disaggregation of Revenue [Line Items]
Revenues	256,017	240,662	499,800	492,116
Export coal revenues | Coal
Disaggregation of Revenue [Line Items]
Revenues	256,017	240,662	499,800	492,116
Export coal revenues | Met Coal
Disaggregation of Revenue [Line Items]
Revenues	250,324	230,293	493,076	474,364
Export coal revenues | Thermal Coal
Disaggregation of Revenue [Line Items]
Revenues	5,693	10,369	6,724	17,752
Domestic coal revenues | Coal
Disaggregation of Revenue [Line Items]
Revenues	137,441	112,453	279,110	262,459
Domestic coal revenues | Met Coal
Disaggregation of Revenue [Line Items]
Revenues	105,235	82,903	205,477	197,591
Domestic coal revenues | Thermal Coal
Disaggregation of Revenue [Line Items]
Revenues	$ 32,206	$ 29,550	$ 73,633	$ 64,868

Revenue - Performance Obligatio

Revenue - Performance Obligations (Details) $ in Thousands	Jun. 30, 2021USD ($)
Disaggregation of Revenue [Line Items]
Estimated coal revenues	$ 116,787
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-07-01
Disaggregation of Revenue [Line Items]
Estimated coal revenues	$ 65,852
Revenue, remaining performance obligation, period	6 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Disaggregation of Revenue [Line Items]
Estimated coal revenues	$ 50,935
Revenue, remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Disaggregation of Revenue [Line Items]
Estimated coal revenues	$ 0
Revenue, remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Disaggregation of Revenue [Line Items]
Estimated coal revenues	$ 0
Revenue, remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Disaggregation of Revenue [Line Items]
Estimated coal revenues	$ 0
Revenue, remaining performance obligation, period	1 year

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss - Changes to Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 200,102	$ 696,122
Ending balance	162,331	409,415
Employee benefit costs
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(111,985)	(58,616)
Other comprehensive income (loss) before reclassifications	8,838	(14,154)
Amounts reclassified from accumulated other comprehensive loss	2,826	3,023
Ending balance	$ (100,321)	$ (69,747)

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Loss - Summary of Amounts Reclassified (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Employee benefit costs:
Miscellaneous income (loss), net	$ (1,847)		$ (395)		$ (3,613)	$ 321
Loss from continuing operations before income taxes	18,582		81,713		51,278	120,087
Income tax	(8)		(33)		(3)	2,155
Net loss	18,991	$ 32,928	238,301	$ 39,808	51,919	278,109
Amounts reclassified from accumulated other comprehensive loss | Amortization of actuarial loss
Employee benefit costs:
Miscellaneous income (loss), net	1,342		934		2,826	1,728
Amounts reclassified from accumulated other comprehensive loss | Settlement
Employee benefit costs:
Miscellaneous income (loss), net	0		95		0	1,295
Amounts reclassified from accumulated other comprehensive loss | Employee benefit costs
Employee benefit costs:
Loss from continuing operations before income taxes	1,342		1,029		2,826	3,023
Income tax	0		0		0	0
Net loss	$ 1,342		$ 1,029		$ 2,826	$ 3,023

Net Loss Per Share (Details)

Net Loss Per Share (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share (in shares)	942,549	1,581,608	948,398	1,492,657
Weighted-average antidilutive securities excluded from computation of earnings per share (in shares)	313,640	9,572	301,684	42,139

Inventories, net (Details)

Inventories, net (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Inventory [Line Items]
Total inventories, net	$ 144,416	$ 108,051
Coal
Inventory [Line Items]
Raw coal	21,071	15,084
Saleable coal	96,768	69,262
Material, supplies and other, net
Inventory [Line Items]
Materials, supplies and other, net	$ 26,577	$ 23,705

Acquired Intangibles - Balance

Acquired Intangibles - Balance Sheet Classification (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Assets	$ 81,610	$ 88,196
Liabilities	(163)	(327)
Net Total	81,447	87,869
Coal supply agreements, net
Finite-Lived Intangible Assets [Line Items]
Net Total	(163)	(327)
Acquired mine permits, net
Finite-Lived Intangible Assets [Line Items]
Net Total	81,610	88,196
Coal supply agreements, net
Finite-Lived Intangible Assets [Line Items]
Liabilities	(163)	(327)
Acquired mine permits, net
Finite-Lived Intangible Assets [Line Items]
Liabilities	0	0
Coal supply agreements, net
Finite-Lived Intangible Assets [Line Items]
Assets	0	0
Acquired mine permits, net
Finite-Lived Intangible Assets [Line Items]
Assets	$ 81,610	$ 88,196

Acquired Intangibles - Amortiza

Acquired Intangibles - Amortization of Intangible Assets (Liabilities) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Finite-Lived Intangible Assets [Line Items]
Amortization of acquired intangibles, net	$ 2,553	$ 1,881	$ 6,422	$ 2,392
Coal supply agreements, net
Finite-Lived Intangible Assets [Line Items]
Amortization of acquired intangibles, net	(82)	(1,439)	(164)	(4,256)
Coal supply agreements, net
Finite-Lived Intangible Assets [Line Items]
Amortization of below-market coal supply agreements	(82)	(1,439)	(164)	(4,274)
Acquired mine permits, net
Finite-Lived Intangible Assets [Line Items]
Amortization of acquired intangibles, net	2,635	3,320	6,586	6,648
Coal supply agreements, net
Finite-Lived Intangible Assets [Line Items]
Amortization of acquired intangibles, net	$ 0	$ 0	$ 0	$ 18

Asset Impairment and Restruct_3

Asset Impairment and Restructuring - Long-Lived Asset Impairment (Details) $ in Thousands	May 31, 2020assetGroup	Feb. 29, 2020assetGroup	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)
Impaired Long-Lived Assets Held and Used [Line Items]
Total from continuing operations			$ 17,390		$ 51,099
Asset impairment related to write-off of prepaid purchase coal			144,348		144,348
Total long-lived asset impairment			161,738		195,447
All Other
Impaired Long-Lived Assets Held and Used [Line Items]
Number of assets impaired | assetGroup	4	3
Total from continuing operations			17,390		18,148
Total long-lived asset impairment				$ 60
Mineral rights, net
Impaired Long-Lived Assets Held and Used [Line Items]
Total from continuing operations			2,241		24,066
Asset impairment related to write-off of prepaid purchase coal			16,364		16,364
Total long-lived asset impairment			18,605		40,430
Property, plant, and equipment, net
Impaired Long-Lived Assets Held and Used [Line Items]
Total from continuing operations			6,496		12,562
Asset impairment related to write-off of prepaid purchase coal			127,984		127,984
Total long-lived asset impairment			134,480		140,546
Acquired mine permits, net
Impaired Long-Lived Assets Held and Used [Line Items]
Total from continuing operations			8,653		14,471
Total long-lived asset impairment			8,653		14,471
Met
Impaired Long-Lived Assets Held and Used [Line Items]
Total from continuing operations			$ 0		$ 32,951
Met | Operating Segments
Impaired Long-Lived Assets Held and Used [Line Items]
Number of assets impaired | assetGroup	3	4

Asset Impairment and Restruct_4

Asset Impairment and Restructuring - Restructuring Expense (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Restructuring Cost and Reserve [Line Items]
Severance and employee-related benefits			$ 940
Strategic Actions with Respect to Two Thermal Coal Mining Complexes
Restructuring Cost and Reserve [Line Items]
Severance and employee-related benefits	$ 20,553		20,553
Other costs	1,882		1,882
Restructuring expense	22,435		22,435
Deferred longwall move expenses	668		668
Allowance for advanced mining royalties	407		407
Allowance for obsolete materials and supplies inventory	807		807
Strategic Actions with Respect to Two Thermal Coal Mining Complexes | Continuing operations
Restructuring Cost and Reserve [Line Items]
Severance and employee-related benefits	2,301		2,301
Other costs	807		807
Restructuring expense	3,108		3,108
Strategic Actions with Respect to Two Thermal Coal Mining Complexes | Discontinued Operations
Restructuring Cost and Reserve [Line Items]
Severance and employee-related benefits	18,252		18,252
Other costs	1,075		1,075
Restructuring expense	19,327		19,327
All Other
Restructuring Cost and Reserve [Line Items]
Severance and employee-related benefits			$ 439
All Other | Strategic Actions with Respect to Two Thermal Coal Mining Complexes
Restructuring Cost and Reserve [Line Items]
Restructuring expense		$ 621
All Other | Strategic Actions with Respect to Two Thermal Coal Mining Complexes | Continuing operations
Restructuring Cost and Reserve [Line Items]
Restructuring expense	$ 3,108

Long-Term Debt - Schedule of Lo

Long-Term Debt - Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Debt discount and issuance costs	$ (11,312)	$ (17,046)
Total long-term debt	579,667	582,527
Less current portion	(29,404)	(28,830)
Long-term debt, net of current portion	550,263	553,697
Term Loan Credit Facility | Term Loan Credit Facility - due June 2024
Debt Instrument [Line Items]
Long-term debt, gross	550,564	553,373
Line of Credit | ABL Facility - due April 2022
Debt Instrument [Line Items]
Long-term debt, gross	0	3,350
Note Payable | LCC Note Payable
Debt Instrument [Line Items]
Long-term debt, gross	27,500	27,500
Note Payable | LCC Water Treatment Obligation
Debt Instrument [Line Items]
Long-term debt, gross	6,250	6,875
Other
Debt Instrument [Line Items]
Long-term debt, gross	$ 6,665	$ 8,475

Long-Term Debt - Narrative (Det

Long-Term Debt - Narrative (Details) - USD ($)	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Term Loan Credit Facility | Term Loan Credit Facility - due June 2024
Debt Instrument [Line Items]
Outstanding borrowings	$ 541,572,000	$ 540,643,000
Current portion of long-term debt	5,618,000	5,618,000
Line of Credit | Revolving Credit Facility | ABL Facility - due April 2022
Debt Instrument [Line Items]
Outstanding borrowings	0	3,350,000
Letters of credit outstanding	$ 128,752,000	$ 123,108,000
Eurocurrency | Term Loan Credit Facility | Term Loan Credit Facility - due June 2024
Debt Instrument [Line Items]
Interest rate at period end	10.00%
Variable interest rate	8.00%

Acquisition-Related Obligatio_3

Acquisition-Related Obligations - Summary of Acquisition-Related Obligations (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Option, Quantitative Disclosures [Line Items]
Discount	$ (768)	$ (1,491)
Total acquisition-related obligations	34,838	39,867
Less current portion	(22,866)	(19,099)
Acquisition-related obligations, net of current portion	11,972	20,768
Contingent Revenue Obligation
Fair Value, Option, Quantitative Disclosures [Line Items]
Total acquisition-related obligations - long-term, gross	23,904	28,967
Total acquisition-related obligations	23,904	28,967
Less current portion	(13,465)	(11,393)
Environmental Settlement Obligations
Fair Value, Option, Quantitative Disclosures [Line Items]
Total acquisition-related obligations - long-term, gross	9,702	10,391
UMWA Funds Settlement Liability
Fair Value, Option, Quantitative Disclosures [Line Items]
Total acquisition-related obligations - long-term, gross	$ 2,000	$ 2,000

Acquisition-Related Obligatio_4

Acquisition-Related Obligations - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Business Acquisition, Contingent Consideration [Line Items]
Acquisition related obligations	$ 34,838	$ 39,867
Acquisition related obligations, current	22,866	19,099
Contingent Revenue Obligation
Business Acquisition, Contingent Consideration [Line Items]
Acquisition related obligations	23,904	28,967
Acquisition related obligations, current	13,465	$ 11,393
Payments for acquisition-related obligations	$ 11,396

Asset Retirement Obligations (D

Asset Retirement Obligations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Total asset retirement obligations at December 31, 2020			$ 165,064
Accretion for the period	$ 6,648	$ 6,569	13,296	$ 13,208
Revisions in estimated cash flows			(17)
Expenditures for the period			(8,592)
Total asset retirement obligations at June 30, 2021	169,751		169,751		$ 165,064
Less current portion	(28,911)		(28,911)
Long-term portion	$ 140,840		$ 140,840		$ 140,074

Fair Value of Financial Instr_3

Fair Value of Financial Instruments and Fair Value Measurements - Summary of Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	$ 573,002	$ 574,052
Carrying Amount | Term Loan Agreement | Term Loan Credit Facility - due June 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	541,572	540,643
Carrying Amount | Line of Credit | ABL Facility - due April 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt		3,350
Carrying Amount | Note Payable | LCC Note Payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	26,046	24,423
Carrying Amount | Note Payable | LCC Water Treatment Obligation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	5,384	5,636
Fair Value, Measurements, Nonrecurring | Total Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	518,743	407,280
Fair Value, Measurements, Nonrecurring | Total Fair Value | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	0	0
Fair Value, Measurements, Nonrecurring | Total Fair Value | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	488,626	379,614
Fair Value, Measurements, Nonrecurring | Total Fair Value | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	30,117	27,666
Fair Value, Measurements, Nonrecurring | Total Fair Value | Term Loan Agreement | Term Loan Credit Facility - due June 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	488,626	379,614
Fair Value, Measurements, Nonrecurring | Total Fair Value | Term Loan Agreement | Term Loan Credit Facility - due June 2024 | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	0	0
Fair Value, Measurements, Nonrecurring | Total Fair Value | Term Loan Agreement | Term Loan Credit Facility - due June 2024 | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	488,626	379,614
Fair Value, Measurements, Nonrecurring | Total Fair Value | Term Loan Agreement | Term Loan Credit Facility - due June 2024 | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	0	0
Fair Value, Measurements, Nonrecurring | Total Fair Value | Line of Credit | ABL Facility - due April 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt		3,057
Fair Value, Measurements, Nonrecurring | Total Fair Value | Line of Credit | ABL Facility - due April 2022 | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt		0
Fair Value, Measurements, Nonrecurring | Total Fair Value | Line of Credit | ABL Facility - due April 2022 | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt		0
Fair Value, Measurements, Nonrecurring | Total Fair Value | Line of Credit | ABL Facility - due April 2022 | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt		3,057
Fair Value, Measurements, Nonrecurring | Total Fair Value | Note Payable | LCC Note Payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	25,172	20,328
Fair Value, Measurements, Nonrecurring | Total Fair Value | Note Payable | LCC Note Payable | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	0	0
Fair Value, Measurements, Nonrecurring | Total Fair Value | Note Payable | LCC Note Payable | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	0	0
Fair Value, Measurements, Nonrecurring | Total Fair Value | Note Payable | LCC Note Payable | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	25,172	20,328
Fair Value, Measurements, Nonrecurring | Total Fair Value | Note Payable | LCC Water Treatment Obligation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	4,945	4,281
Fair Value, Measurements, Nonrecurring | Total Fair Value | Note Payable | LCC Water Treatment Obligation | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	0	0
Fair Value, Measurements, Nonrecurring | Total Fair Value | Note Payable | LCC Water Treatment Obligation | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	0	0
Fair Value, Measurements, Nonrecurring | Total Fair Value | Note Payable | LCC Water Treatment Obligation | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total long term debt	$ 4,945	$ 4,281

Fair Value of Financial Instr_4

Fair Value of Financial Instruments and Fair Value Measurements - Acquisition-related Obligations at Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related obligations	$ 10,934	$ 10,899
Carrying Amount | UMWA Funds Settlement Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related obligations	1,823	1,662
Carrying Amount | Environmental Settlement Obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related obligations	9,111	9,237
Fair Value, Measurements, Nonrecurring | Total Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related obligations	10,561	9,186
Fair Value, Measurements, Nonrecurring | Total Fair Value | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related obligations	0	0
Fair Value, Measurements, Nonrecurring | Total Fair Value | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related obligations	0	0
Fair Value, Measurements, Nonrecurring | Total Fair Value | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related obligations	10,561	9,186
Fair Value, Measurements, Nonrecurring | Total Fair Value | UMWA Funds Settlement Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related obligations	1,797	1,426
Fair Value, Measurements, Nonrecurring | Total Fair Value | UMWA Funds Settlement Liability | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related obligations	0	0
Fair Value, Measurements, Nonrecurring | Total Fair Value | UMWA Funds Settlement Liability | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related obligations	0	0
Fair Value, Measurements, Nonrecurring | Total Fair Value | UMWA Funds Settlement Liability | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related obligations	1,797	1,426
Fair Value, Measurements, Nonrecurring | Total Fair Value | Environmental Settlement Obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related obligations	8,764	7,760
Fair Value, Measurements, Nonrecurring | Total Fair Value | Environmental Settlement Obligations | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related obligations	0	0
Fair Value, Measurements, Nonrecurring | Total Fair Value | Environmental Settlement Obligations | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related obligations	0	0
Fair Value, Measurements, Nonrecurring | Total Fair Value | Environmental Settlement Obligations | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related obligations	$ 8,764	$ 7,760

Fair Value of Financial Instr_5

Fair Value of Financial Instruments and Fair Value Measurements - Schedule of Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Contingent Revenue Obligation	$ 23,904	$ 28,967
Trading securities	31,189	22,498
Quoted Prices in Active Markets (Level 1)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Contingent Revenue Obligation	0	0
Trading securities	29,311	20,092
Significant Other Observable Inputs (Level 2)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Contingent Revenue Obligation	0	0
Trading securities	1,878	2,406
Significant Unobservable Inputs (Level 3)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Contingent Revenue Obligation	23,904	28,967
Trading securities	$ 0	$ 0

Fair Value of Financial Instr_6

Fair Value of Financial Instruments and Fair Value Measurements - Level 3 of the Fair Value Hierarchy (Details) - Significant Unobservable Inputs (Level 3) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning balance	$ 28,967	$ 52,427
Payments	(11,396)	(14,710)
Loss (Gain) Recognized in Earnings	6,333	(17,049)
Transfer In (Out) of Level 3 Fair Value Hierarchy	0	0
Ending balance	$ 23,904	$ 20,668

Fair Value of Financial Instr_7

Fair Value of Financial Instruments and Fair Value Measurements - Level 3 Fair Value Measurements (Details) $ in Billions	Jun. 30, 2021USD ($)	Dec. 31, 2020USD ($)
Black Scholes | Forecasted future revenue | Minimum | Contingent Revenue Obligation
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition-related obligation, measurement input	1.1	0.9
Black Scholes | Forecasted future revenue | Maximum | Contingent Revenue Obligation
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition-related obligation, measurement input	1.2	1.1
Black Scholes | Stated royalty rate | Minimum | Contingent Revenue Obligation
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition-related obligation, measurement input	0.010	0.010
Black Scholes | Stated royalty rate | Maximum | Contingent Revenue Obligation
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition-related obligation, measurement input	0.015	0.015
Black Scholes | Annualized volatility | Minimum | Contingent Revenue Obligation
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition-related obligation, measurement input	0.176	0.194
Black Scholes | Annualized volatility | Maximum | Contingent Revenue Obligation
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition-related obligation, measurement input	0.401	0.521
Black Scholes | Annualized volatility | Weighted Average | Contingent Revenue Obligation
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Acquisition-related obligation, measurement input	0.290	0.280
Fair Value, Measurements, Recurring | Discounted cash flow | Significant Unobservable Inputs (Level 3) | Discount rate | Notes Payable, UMWA Funds Settlement Liability, Enviromental Settlement Obligations, and Reclaimation Funding Liability,
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt and acquisition-related obligation, measurement input	0.22	0.34
Line of Credit | Fair Value, Measurements, Recurring | Discounted cash flow | ABL Facility - due April 2022 | Significant Unobservable Inputs (Level 3) | Discount rate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Debt, measurement input		0.09

Income Taxes (Details)

Income Taxes (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income tax expense	$ 8,000	$ 33,000	$ 3,000	$ (2,155,000)
Income (loss) from continuing operations before income taxes	(18,582,000)	$ (81,713,000)	(51,278,000)	$ (120,087,000)
Current estimated federal income tax liability	$ 0		0
Increase in deferred tax asset valuation allowance			$ 6,184,000

Employee Benefit Plans - Schedu

Employee Benefit Plans - Schedule of Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Pension
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Interest cost	$ 3,362	$ 4,656	$ 6,784	$ 9,391
Expected return on plan assets	(7,119)	(6,748)	(14,366)	(13,560)
Amortization of net actuarial loss (gain)	734	521	1,609	990
Settlement	0	63	0	1,230
Net periodic expense	(3,023)	(1,508)	(5,973)	(1,949)
Black Lung
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	739	492	1,478	980
Interest cost	607	775	1,214	1,597
Expected return on plan assets	(14)	(14)	(28)	(27)
Amortization of net actuarial loss (gain)	522	286	1,044	501
Net periodic expense	$ 1,854	$ 1,539	$ 3,708	$ 3,051

Employee Benefit Plans - Narrat

Employee Benefit Plans - Narrative (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2021USD ($)	Jun. 30, 2021USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Decrease in liability for pension obligations	$ 8,838
Pension | American Rescue Plan Act
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Pension plan, employer contributions		$ 3,701
Pension plan, expected employer contributions	$ 7,664	$ 7,664

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2021USD ($)T	Jun. 30, 2021USD ($)T	Dec. 31, 2021USD ($)T	Dec. 31, 2022USD ($)T	Dec. 31, 2020USD ($)	Feb. 21, 2020USD ($)	Feb. 20, 2020USD ($)
Long-term Purchase Commitment [Line Items]
Income tax receivable	$ 64,160	$ 64,160
Income tax receivable related to NOL carryback claim	5,385	5,385
Black Lung
Long-term Purchase Commitment [Line Items]
Collateral for self insurance black lunch obligations						$ 65,700	$ 2,600
Reclamation-related obligations
Long-term Purchase Commitment [Line Items]
Collateral supporting guarantees	42,211	42,211
Surety Bond
Long-term Purchase Commitment [Line Items]
Guarantees	211,694	211,694
Guarantor obligations attributable to discontinued operations	30	30
Revolving Credit Facility | Line of Credit | Credit and Security Agreement
Long-term Purchase Commitment [Line Items]
Letters of credit outstanding	613	613
Revolving Credit Facility | Line of Credit | ABL Facility - due April 2022
Long-term Purchase Commitment [Line Items]
Letters of credit outstanding	$ 128,752	$ 128,752			$ 123,108
Cumberland Back-to-Back Coal Supply Agreements
Long-term Purchase Commitment [Line Items]
Purchase and sale contingency, mass purchased and sold (in tons) | T	760,000	1,460,000
Purchase and sale contingency, mass purchased and sold, amount	$ 29,487	$ 56,553
Cumberland Back-to-Back Coal Supply Agreements | Forecast
Long-term Purchase Commitment [Line Items]
Purchase and sale contingency, mass purchased and sold (in tons) | T			1,226,000	2,615,000
Purchase and sale contingency, mass purchased and sold, amount			$ 47,803	$ 101,990
Commitment of Fixed Priced Tons from Vendors with Historical Performance Resulting in Less Than 20% of Committed Tonnage Being Delivered
Long-term Purchase Commitment [Line Items]
Minimum quantities to be purchased, 2021	3,230	3,230
Coal Purchase Agreements
Long-term Purchase Commitment [Line Items]
Minimum quantities to be purchased, 2021	33,477	33,477
Shipping
Long-term Purchase Commitment [Line Items]
Minimum quantities to be shipped, 2022	$ 32,940	$ 32,940

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Restricted Cash Deposits (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Long-term Purchase Commitment [Line Items]
Total restricted cash	$ 96,552	$ 105,344
Less current portion	(3,794)	(9,311)	$ (3,720)
Long-term restricted cash	92,758	96,033	$ 109,930
Workers' compensation and black lung obligations
Long-term Purchase Commitment [Line Items]
Total restricted cash	63,096	69,725
Reclamation-related obligations
Long-term Purchase Commitment [Line Items]
Total restricted cash	6,989	8,445
Financial payments and other performance obligations
Long-term Purchase Commitment [Line Items]
Total restricted cash	22,673	17,863
Contingent revenue obligation escrow
Long-term Purchase Commitment [Line Items]
Total restricted cash	$ 3,794	$ 9,311

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Restricted Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Long-term Purchase Commitment [Line Items]
Total restricted investments	$ 31,442	$ 23,768
Restricted investments, trading	31,189	22,498
Restricted investments, held-to-maturity	253	1,270
Workers' compensation and black lung obligations
Long-term Purchase Commitment [Line Items]
Total restricted investments	210	51
Reclamation-related obligations
Long-term Purchase Commitment [Line Items]
Total restricted investments	29,195	22,233
Financial payments and other performance obligations
Long-term Purchase Commitment [Line Items]
Total restricted investments	$ 2,037	$ 1,484

Commitments and Contingencies_4

Commitments and Contingencies - Cash Deposits Held by Third Parties (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Long-term Purchase Commitment [Line Items]
Total deposits	$ 7,696	$ 28,247
Workers' compensation and black lung obligations
Long-term Purchase Commitment [Line Items]
Total deposits	35	0
Reclamation-related obligations
Long-term Purchase Commitment [Line Items]
Total deposits	6,027	25,633
Financial payments and other performance obligations
Long-term Purchase Commitment [Line Items]
Total deposits	732	1,596
Other operating agreements
Long-term Purchase Commitment [Line Items]
Total deposits	$ 902	$ 1,018

Segment Information - Schedule

Segment Information - Schedule of Operating Results and Capital Expenditures (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)mineplantsegment	Jun. 30, 2020USD ($)	Dec. 31, 2020segment
Segment Reporting Information [Line Items]
Number of reportable segments | segment			1		2
Total revenues	$ 395,275	$ 353,940	$ 781,528	$ 756,744
Depreciation, depletion and amortization	27,304	47,069	55,742	94,685
Amortization of acquired intangibles, net	2,553	1,881	6,422	2,392
Adjusted EBITDA	39,917	7,145	68,801	63,642
Capital expenditures	17,644	30,658	38,039	66,921
Operating Segments | Met
Segment Reporting Information [Line Items]
Total revenues	377,937	316,534	737,815	679,293
Depreciation, depletion and amortization	25,686	38,779	52,222	80,501
Amortization of acquired intangibles, net	2,635	2,759	6,686	5,340
Adjusted EBITDA	46,786	17,518	79,368	86,636
Capital expenditures	17,203	27,647	$ 37,526	60,781
Operating Segments | Met | Virginia
Segment Reporting Information [Line Items]
Number of active mines | mine			5
Number of preparation plants | plant			2
Operating Segments | Met | West Virginia
Segment Reporting Information [Line Items]
Number of active mines | mine			14
Number of preparation plants | plant			5
All Other
Segment Reporting Information [Line Items]
Total revenues	17,338	37,406	$ 43,713	77,451
Depreciation, depletion and amortization	1,618	8,290	3,520	14,184
Amortization of acquired intangibles, net	(82)	(878)	(264)	(2,948)
Adjusted EBITDA	(6,869)	(10,373)	(10,567)	(22,994)
Capital expenditures	$ 441	$ 3,011	$ 513	$ 6,140
All Other | West Virginia
Segment Reporting Information [Line Items]
Number of active mines | mine			1
Number of preparation plants | plant			1

Segment Information - Reconcili

Segment Information - Reconciliation of Net Income (Loss) to Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net loss from continuing operations	$ (18,590)	$ (81,746)	$ (51,281)	$ (117,932)
Interest expense	17,962	19,316	35,952	37,492
Interest income	(104)	(5,530)	(268)	(6,498)
Income tax expense (benefit)	8	33	3	(2,155)
Depreciation, depletion and amortization	27,304	47,069	55,742	94,685
Non-cash stock compensation expense	979	1,044	3,163	3,122
Mark-to-market adjustment for acquisition-related obligations	3,157	(2,052)	6,333	(17,049)
Accretion on asset retirement obligations	6,648	6,569	13,296	13,208
Asset impairment and restructuring	0	20,498	(561)	54,207
Management restructuring costs				940
Loss on partial settlement of benefit obligations		63		1,230
Amortization of acquired intangibles, net	2,553	1,881	6,422	2,392
Adjusted EBITDA	39,917	7,145	68,801	63,642
Strategic Actions with Respect to Two Thermal Coal Mining Complexes
Segment Reporting, Other Significant Reconciling Item [Line Items]
Management restructuring costs		20,553		20,553
Operating Segments | Met
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net loss from continuing operations	15,042	(27,097)	13,604	(38,682)
Interest expense	40	(377)	83	(1,306)
Interest income	0	(3)	(5)	(61)
Income tax expense (benefit)	0	0	0	0
Depreciation, depletion and amortization	25,686	38,779	52,222	80,501
Non-cash stock compensation expense	6	(94)	16	305
Mark-to-market adjustment for acquisition-related obligations	0	0	0	0
Accretion on asset retirement obligations	3,377	3,551	6,762	7,087
Asset impairment and restructuring		0	0	32,951
Management restructuring costs				501
Loss on partial settlement of benefit obligations		0		0
Amortization of acquired intangibles, net	2,635	2,759	6,686	5,340
Adjusted EBITDA	46,786	17,518	79,368	86,636
All Other
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net loss from continuing operations	(33,632)	(54,649)	(64,885)	(79,250)
Interest expense	17,922	19,693	35,869	38,798
Interest income	(104)	(5,527)	(263)	(6,437)
Income tax expense (benefit)	8	33	3	(2,155)
Depreciation, depletion and amortization	1,618	8,290	3,520	14,184
Non-cash stock compensation expense	973	1,138	3,147	2,817
Mark-to-market adjustment for acquisition-related obligations	3,157	(2,052)	6,333	(17,049)
Accretion on asset retirement obligations	3,271	3,018	6,534	6,121
Asset impairment and restructuring		20,498	(561)	21,256
Management restructuring costs				439
Loss on partial settlement of benefit obligations		63		1,230
Amortization of acquired intangibles, net	(82)	(878)	(264)	(2,948)
Adjusted EBITDA	$ (6,869)	$ (10,373)	$ (10,567)	$ (22,994)

Segment Information - Revenue f

Segment Information - Revenue from External Customers (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Coal revenues	$ 393,458	$ 353,115	$ 778,910	$ 754,575
Export coal revenues
Revenues from External Customers and Long-Lived Assets [Line Items]
Coal revenues	$ 256,017	$ 240,662	$ 499,800	$ 492,116
Geographic Concentration Risk | Export coal revenues | Export Coal Revenue
Revenues from External Customers and Long-Lived Assets [Line Items]
Concentration risk percentage	65.00%	68.00%	64.00%	65.00%

Uncategorized Items - amr-20210

Label	Element	Value
Accounting Standards Update [Extensible Enumeration]	us-gaap_AccountingStandardsUpdateExtensibleList	Accounting Standards Update 2016-13 [Member]