Arch Resources (ARCH) 10-Q 23 Oct 20 2020 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2020	Oct. 23, 2020
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	1-13105
Entity Registrant Name	Arch Resources, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	43-0921172
Entity Central Index Key	0001037676
Entity Address, Address Line One	One CityPlace Drive
Entity Address, Address Line Two	Suite 300
Entity Address, City or Town	St. Louis
Entity Address, State or Province	MO
Entity Address, Postal Zip Code	63141
City Area Code	314
Local Phone Number	994-2700
Title of 12(b) Security	Common stock, $.01 par value
Trading Symbol	ARCH
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business Company	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		15,147,289
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3

Condensed Consolidated Income S

Condensed Consolidated Income Statements - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues	$ 382,261	$ 619,467	$ 1,107,014	$ 1,744,872
Costs, expenses and other operating
Cost of sales (exclusive of items shown separately below)	345,539	491,004	1,036,886	1,380,563
Depreciation, depletion and amortization	32,630	30,249	94,105	82,122
Accretion on asset retirement obligations	4,947	5,137	14,939	15,411
Change in fair value of coal derivatives and coal trading activities, net	2,649	1,530	3,263	(19,851)
Selling, general and administrative expenses	21,541	24,566	64,024	73,864
Costs related to proposed joint venture with Peabody Energy	4,423	3,754	15,938	6,772
Asset impairment	163,088		163,088
Severance costs related to voluntary separation plan	18		13,283
Gain on property insurance recovery related to Mountain Laurel longwall			(23,518)
(Gain) loss on divestitures			(1,369)	4,304
Preference Rights Lease Application settlement income		(39,000)	(23,518)	(39,000)
Other operating income, net	(4,894)	(4,254)	(16,768)	(9,143)
Costs, expenses and other operating	569,941	512,986	1,363,871	1,495,042
Income (loss) from operations	(187,680)	106,481	(256,857)	249,830
Interest expense, net
Interest expense	(2,989)	(4,049)	(9,900)	(12,856)
Interest and investment income	459	3,709	3,511	7,940
Interest expense, net	(2,530)	(340)	(6,389)	(4,916)
Income (loss) before nonoperating expenses	(190,210)	106,141	(263,246)	244,914
Nonoperating (expenses) income
Non-service related pension and postretirement benefit costs	(878)	975	(3,076)	(2,127)
Reorganization items, net			26	71
Nonoperating (expenses) income	(878)	975	(3,050)	(2,056)
Income (loss) before income taxes	(191,088)	107,116	(266,296)	242,858
Provision for (benefit from) income taxes	379	347	(206)	508
Net income (loss)	$ (191,467)	$ 106,769	$ (266,090)	$ 242,350
Net income (loss) per common share
Basic earnings (loss) per common share (in dollars per share)	$ (12.64)	$ 6.79	$ (17.57)	$ 14.61
Diluted earnings (loss) per common share (in dollars per share)	$ (12.64)	$ 6.34	$ (17.57)	$ 13.66
Weighted average shares outstanding
Basic weighted average shares outstanding (in shares)	15,147	15,736	15,144	16,591
Diluted weighted average shares outstanding (in shares)	15,147	16,852	15,144	17,744
Dividends declared per common share (in dollars per share)		$ 0.45	$ 0.50	$ 1.35
Dal-Tex and Briar Branch Properties
Costs, expenses and other operating
(Gain) loss on divestitures			$ (1,369)	$ 4,304

Condensed Consolidated Statemen

Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income (loss)	$ (191,467)	$ 106,769	$ (266,090)	$ 242,350
Derivative instruments
Comprehensive income (loss) before tax	476	(2,360)	(1,830)	(2,421)
Other comprehensive income (loss), derivative instruments, net of tax	476	(2,360)	(1,830)	(2,421)
Pension, postretirement and other post-employment benefits
Comprehensive income (loss) before tax	4,164	(4,019)	(12,439)	(1,117)
Other comprehensive income (loss), pension, postretirement and other post-employment benefits, net of tax	4,164	(4,019)	(12,439)	(1,117)
Available-for-sale securities
Comprehensive income (loss) before tax	(255)	(98)	(189)	553
Other comprehensive income (loss), available-for-sale securities, net of tax	(255)	(98)	(189)	553
Total other comprehensive income (loss)	4,385	(6,477)	(14,458)	(2,985)
Total comprehensive income (loss)	$ (187,082)	$ 100,292	$ (280,548)	$ 239,365

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 156,655	$ 153,020
Short term investments	63,128	135,667
Restricted cash	13,919
Trade accounts receivable (net of $1,303 allowance at September 30, 2020)	127,292	168,125
Other receivables	2,880	21,143
Inventories	143,396	130,898
Other current assets	55,712	97,894
Total current assets	562,982	706,747
Property, plant and equipment, net	964,472	984,509
Other assets
Equity investments	70,275	105,588
Other noncurrent assets	55,608	70,912
Total other assets	125,883	176,500
Total assets	1,653,337	1,867,756
Current Liabilities
Accounts payable	99,110	133,060
Accrued expenses and other current liabilities	141,021	157,167
Current maturities of debt	25,987	20,753
Total current liabilities	266,118	310,980
Long-term debt	368,278	290,066
Asset retirement obligations	239,614	242,432
Accrued pension benefits	6,108	5,476
Accrued postretirement benefits other than pension	85,642	80,567
Accrued workers' compensation	219,851	215,599
Other noncurrent liabilities	102,080	82,100
Total liabilities	1,287,691	1,227,220
Stockholders' equity
Common stock, $0.01 par value, authorized 300,000 shares, issued 25,235 and 25,220 shares at September 30, 2020 and December 31, 2019, respectively	252	252
Paid-in capital	744,112	730,551
Retained earnings	457,432	731,425
Treasury stock, 10,088 shares at September 30, 2020 and December 31, 2019, respectively, at cost	(827,381)	(827,381)
Accumulated other comprehensive income (loss)	(8,769)	5,689
Total stockholders' equity	365,646	640,536
Total liabilities and stockholders' equity	$ 1,653,337	$ 1,867,756

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Trade accounts receivable, allowance	$ 1,303
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares issued (in shares)	25,235,000	25,220,000
Treasury stock, shares (in shares)	10,088,000	10,088,000

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019
Operating activities
Net income (loss)	$ (191,467)	$ (266,090)	$ 242,350
Adjustments to reconcile to cash from operating activities:
Depreciation, depletion and amortization	32,630	94,105	82,122
Accretion on asset retirement obligations	4,947	14,939	15,411
Deferred income taxes		14,227	13,680
Employee stock-based compensation expense		13,907	17,305
Amortization relating to financing activities		3,189	2,757
Gain on property insurance recovery related to Mountain Laurel longwall		(23,518)
Gains on disposals and divestitures, net		(3,460)	(818)
Asset impairment	163,088	163,088
Preference Rights Lease Application settlement income		(23,518)	(39,000)
Changes in:
Receivables		47,416	(4,622)
Inventories		(12,499)	(46,073)
Accounts payable, accrued expenses and other current liabilities		(50,474)	1,569
Income taxes, net		22,855	32,440
Other		38,229	16,932
Cash provided by operating activities		55,914	334,053
Investing activities
Capital expenditures	(57,100)	(205,661)	(137,396)
Minimum royalty payments		(1,186)	(1,187)
Proceeds from disposals and divestitures		856	1,799
Purchases of short term investments		(76,593)	(158,578)
Proceeds from sales of short term investments		148,670	146,170
Investments in and advances to affiliates, net		(1,549)	(4,810)
Proceeds from property insurance recovery related to Mountain Laurel longwall		23,518
Cash used in investing activities		(111,945)	(154,002)
Financing activities
Payments on term loan due 2024		(2,250)	(2,250)
Proceeds from equipment financing		53,611
Proceeds from tax exempt bonds		53,090
Net payments on other debt		(19,347)	(12,077)
Debt financing costs		(3,528)
Dividends paid		(7,645)	(22,264)
Purchases of treasury stock			(232,999)
Payments for taxes related to net share settlement of equity awards		(346)
Other			30
Cash provided by (used in) financing activities		73,585	(269,560)
Increase (decrease) in cash and cash equivalents, including restricted cash		17,554	(89,509)
Cash and cash equivalents, including restricted cash, beginning of period	153,020		264,937
Cash and cash equivalents, including restricted cash, end of period	170,574	170,574	175,428
Cash and cash equivalents, including restricted cash, end of period
Cash and cash equivalents, including restricted cash	$ 170,574	$ 170,574	$ 175,428

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Common Stock	Paid-in Capital	Retained Earnings	Treasury Stock, at cost	Accumulated Other Comprehensive Income (Loss)	Total
Beginning Balance at Dec. 31, 2018	$ 250	$ 717,492	$ 527,666	$ (583,883)	$ 43,296	$ 704,821
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends on common shares			(8,111)			(8,111)
Total comprehensive income (loss)			72,741		3,094	75,835
Employee stock-based compensation		5,651				5,651
Purchase of common stock under share repurchase program				(78,249)		(78,249)
Ending Balance at Mar. 31, 2019	250	723,143	592,296	(662,132)	46,390	699,947
Beginning Balance at Dec. 31, 2018	250	717,492	527,666	(583,883)	43,296	704,821
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)						239,365
Ending Balance at Sep. 30, 2019	250	734,829	746,928	(816,882)	40,311	705,436
Beginning Balance at Mar. 31, 2019	250	723,143	592,296	(662,132)	46,390	699,947
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends on common shares			(7,696)			(7,696)
Total comprehensive income (loss)			62,840		398	63,238
Employee stock-based compensation		5,822				5,822
Purchase of common stock under share repurchase program				(63,392)		(63,392)
Warrants exercised		31				31
Ending Balance at Jun. 30, 2019	250	728,996	647,440	(725,524)	46,788	697,950
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends on common shares			(7,281)			(7,281)
Total comprehensive income (loss)			106,769		(6,477)	100,292
Employee stock-based compensation		5,833				5,833
Purchase of common stock under share repurchase program				(91,358)		(91,358)
Ending Balance at Sep. 30, 2019	250	734,829	746,928	(816,882)	40,311	705,436
Beginning Balance at Dec. 31, 2019	252	730,551	731,425	(827,381)	5,689	640,536
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends on common shares			(7,834)			(7,834)
Total comprehensive income (loss)			(25,299)		(17,403)	(42,702)
Employee stock-based compensation		4,045				4,045
Common stock withheld related to net share settlement of equity awards		(281)				(281)
Ending Balance at Mar. 31, 2020	252	734,315	698,292	(827,381)	(11,714)	593,764
Beginning Balance at Dec. 31, 2019	252	730,551	731,425	(827,381)	5,689	640,536
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock-based compensation		4,891				4,891
Common stock withheld related to net share settlement of equity awards		(50)				(50)
Dividend Equivalents earned on RSU grants			(59)			(59)
Ending Balance at Jun. 30, 2020	252	739,156	648,909	(827,381)	(13,154)	547,782
Beginning Balance at Dec. 31, 2019	252	730,551	731,425	(827,381)	5,689	640,536
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)						(280,548)
Ending Balance at Sep. 30, 2020	252	744,112	457,432	(827,381)	(8,769)	365,646
Beginning Balance at Mar. 31, 2020	252	734,315	698,292	(827,381)	(11,714)	593,764
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)			(49,324)		(1,440)	(50,764)
Ending Balance at Jun. 30, 2020	252	739,156	648,909	(827,381)	(13,154)	547,782
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)			(191,467)		4,385	(187,082)
Employee stock-based compensation		4,971				4,971
Common stock withheld related to net share settlement of equity awards		(15)				(15)
Dividend Equivalents earned on RSU grants			(10)			(10)
Ending Balance at Sep. 30, 2020	$ 252	$ 744,112	$ 457,432	$ (827,381)	$ (8,769)	$ 365,646

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders' Equity (Deficit) (Parenthetical) - $ / shares	3 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Statement of Stockholders' Equity [Abstract]
Dividends declared per common share (in dollars per share)	$ 0.45	$ 0.45	$ 0.45
Purchase of shares of common stock under share repurchase program (in shares)	1,169,597	697,255	872,317

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2020
Basis of Presentation
Basis of Presentation	1. The accompanying unaudited condensed consolidated financial statements include the accounts of Arch Resources, Inc. (“Arch Resources”) and its subsidiaries (“Arch” or the “Company”). Unless the context indicates otherwise, the terms “Arch” and the “Company” are used interchangeably in this Quarterly Report on Form 10-Q. The Company’s primary business is the production of metallurgical and thermal coal from surface and underground mines located throughout the United States, for sale to steel producers, utility companies, industrial accounts both in the United States and around the world. The Company currently operates mining complexes in West Virginia, Illinois, Wyoming and Colorado. All subsidiaries are wholly-owned. Intercompany transactions and accounts have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States for interim financial reporting and U.S. Securities and Exchange Commission regulations. In the opinion of management, all adjustments, consisting of normal, recurring accruals considered necessary for a fair presentation, have been included. Results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of results to be expected for the year ending December 31, 2020. These financial statements should be read in conjunction with the audited financial statements and related notes as of and for the year ended December 31, 2019 included in the Company’s Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission. Effective May 15, 2020, Arch Coal, Inc. announced that its name changed to Arch Resources, Inc.

Accounting Policies

Accounting Policies	9 Months Ended
	Sep. 30, 2020
Accounting Policies
Accounting Policies	2. Recently Adopted Accounting Guidance In June 2016, the FASB issued ASU 2016-13, “Financial Instruments-Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments,” and also issued subsequent amendments to the initial guidance under ASU 2018-19, ASU 2019-04 and ASU 2019-05. The standard modifies the measurement approach for credit losses on financial instruments, including trade receivables, from an incurred loss method to a current expected credit loss method, otherwise known as “CECL.” The standard requires the measurement of expected credit losses to be based on relevant information, including historical experience, current conditions and a forecast that is supportable. The Company adopted the standard in the first quarter of 2020, with minimal impact to the Company’s financial results. As part of the adoption, the Company reviewed its portfolio of available-for-sale debt securities in an unrealized loss position, and assessed whether it intends to sell, or it is more likely than not that it will be required to sell before recovery of its amortized cost basis. The Company determined that it currently does not intend to sell these securities before recovery of their amortized cost basis. Additionally, the Company evaluated whether the decline in fair value has resulted from credit losses or other factors by considering the extent to which the fair value is less than amortized cost, any changes to the rating of the security by a rating agency, and adverse conditions specifically related to the security, among other factors. If this assessment indicates that a credit loss exists, the Company compares the present value of the cash flows expected to be collected against the amortized cost basis. A credit loss is recorded if the present value of the cash flows is less than the amortized cost basis, limited by the amount that the fair value is less than the amortized cost basis. Upon adoption, the Company did not record an allowance for credit losses on its available-for-sale debt securities. Additionally, the Company reviewed its open trade receivables arising from contractual coal sales. As part of its analysis, the Company performs periodic credit reviews of all active customers, reviews all trade receivables greater than 90 days past due, calculates historical loss rates and reviews current payment trends of all customers. ​ Recent Accounting Guidance Issued Not Yet Effective In December 2019, the FASB issued ASU 2019- 12, “Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes.” ASU 2019- 12 eliminates certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. The ASU is effective for public companies for fiscal years beginning after December 15, 2020, and interim periods therein with early adoption permitted. The Company is reviewing the provisions of the standard but does not expect a significant impact to the Company's financial statements. In March 2020, the FASB issued ASU 2020-04, "Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting." The amendments provide optional guidance for a limited time to ease the potential burden in accounting for reference rate reform. The new guidance provides optional expedients and exceptions for applying U.S. GAAP to contracts, hedging relationships and other transactions affected by reference rate reform if certain criteria are met. The amendments apply only to contracts and hedging relationships that reference LIBOR or another reference rate expected to be discontinued due to reference rate reform. These amendments are effective immediately and may be applied prospectively to contract modifications made and hedging relationships entered into or evaluated on or before December 31, 2022. We are currently evaluating our contracts and the optional expedients provided by the new standard.

Joint Venture with Peabody Ener

Joint Venture with Peabody Energy	9 Months Ended
	Sep. 30, 2020
Joint Venture with Peabody Energy
Joint Venture with Peabody Energy	3. On June 18, 2019, Arch Coal, Inc. (now Arch Resources) entered into a definitive implementation agreement (the “Implementation Agreement”) with Peabody Energy Corporation (“Peabody”), to establish a joint venture that would have combined the respective Powder River Basin and Colorado mining operations of Arch Resources and Peabody. Pursuant to the terms of the Implementation Agreement, Arch Resources would have held a 33.5% economic interest, and Peabody would have held a 66.5% economic interest in the joint venture. On February 26, 2020, the Federal Trade Commission (“FTC”) filed an administrative complaint challenging the proposed joint venture alleging the transaction will eliminate competition between Arch Resources and Peabody, the two major competitors in the market for thermal coal in the Southern Powder River Basin and the two largest coal-mining companies in the United States. The FTC filed a temporary restraining order and preliminary injunction in the U.S. District Court for the Eastern District of Missouri, to maintain the status quo pending an administrative trial on the merits. Between July 14 and July 23, 2020, the U.S. District Court conducted an evidentiary hearing, during which both sides further presented their evidence and arguments. On September 29, 2020, the U.S. District Court upheld the FTC’s decision to block the joint venture. Subsequently, the Company and Peabody jointly terminated the joint venture. The Company has incurred expenses of $4.4 million and $15.9 million for the three and nine months ended September 30, 2020, respectively, associated with the regulatory approval process related to the joint venture. Costs of million were incurred for the three and nine months ended September 30, 2019, respectively.

Gain on Property Insurance Reco

Gain on Property Insurance Recovery Related to Mountain Laurel Longwall	9 Months Ended
	Sep. 30, 2020
Gain on Property Insurance Recovery Related to Mountain Laurel Longwall
Gain on Property Insurance Recovery Related to Mountain Laurel Longwall	4. Gain on Property Insurance Recovery Related to Mountain Laurel Longwall The Company recorded a $23.5 million gain related to a property insurance recovery on the longwall shields at its Mountain Laurel operation during the nine months ended September 30, 2020. As a result of geologic conditions in the final longwall panel, Mountain Laurel was unable to recover 123 of the longwall system’s 176 hydraulic shields. All of the cash associated with the insurance recovery was received by the end of the second quarter of 2020.

Severance Costs Related To Volu

Severance Costs Related To Voluntary Separation Plan	9 Months Ended
	Sep. 30, 2020
Severance Costs Related To Voluntary Separation Plan
Severance Costs Related To Voluntary Separation Plan	5. The Company recorded $13.3 million of employee severance expense related to a voluntary separation plan during the nine months ended September 30, 2020. During the first and second quarters of 2020,

Divestitures

Divestitures	9 Months Ended
	Sep. 30, 2020
Divestitures
Divestitures	6. Divestitures During the second quarter of 2020, various Dal-Tex and Briar Branch properties in West Virginia were sold to Condor Holdings, LLC. No consideration was received for the sale and a gain of $1.4 million was recorded representing the net liabilities sold. On September 14, 2017, the Company sold Lone Mountain Processing, LLC and two idled mining companies, Cumberland River Coal LLC and Powell Mountain Energy LLC to Revelation Energy LLC, and recorded a gain on the transaction in that year of $21.3 million. Under the terms of the purchase agreement, Revelation assumed certain traumatic workers compensation claims and pneumoconiosis (occupational disease) benefits. On July 1, 2019, Blackjewel LLC and four affiliates, including Revelation Energy LLC filed for Chapter 11 bankruptcy. As a result of the bankruptcy, the Company recorded a $4.3 million charge for these claims as of September 30, 2019.

Preference Rights Lease Applica

Preference Rights Lease Application Settlement Income	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies
Preference Rights Lease Application Settlement Income	7. Preference Rights Lease Application Settlement Income The Company recorded a $39 million gain during the third quarter of 2019 related to a settlement with the United States Department of Interior over a long-standing dispute, dating back to the 1970’s, on the valuation and disposition of Preference Rights Lease Applications that Arch controlled in northwestern New Mexico with a joint venture partner. As part of the settlement, Arch received $67.0 million in the form of royalty credits on its federal coal leases which will be used to settle 50 % of the Company’s monthly royalty obligations. The Company expects to realize the royalty credits beginning in September 2019 through the next 18 - 24 months depending on market conditions. Additionally, as part of the settlement, the Company made a one-time payment of $27.0 million during October 2019 to its’ partner in the venture for its ownership interest in the underlying mineral reserves, as well as paid $1.0 million in closing fees. As of September 30, 2020, the Company realized $8.7 million and $25.8 million towards its royalty obligations for the three months and nine months ended September 30, 2020. The Company realized a credit of $5 million towards its royalty obligations during the quarter ended September 30, 2019. The remaining receivable balance outstanding at September 30, 2020 is $27.8 million which is expected to be received over the next three quarters.

Asset Impairment

Asset Impairment	9 Months Ended
	Sep. 30, 2020
Asset Impairment
Asset Impairment	8. Asset Impairment The following table summarizes the amounts reflected on the line “Asset impairment” in the Condensed Consolidated Statements of Operations: ​ ​ ​ ​ ​ ​ September 30, Description 2020 ​ ​ (In thousands) Coal lands and mineral rights ​ $ 33,197 Plant and equipment ​ 43,197 Deferred development ​ ​ 50,527 Equity Investment ​ ​ 36,167 ​ ​ $ 163,088 ​ ​ ​ ​ ​ The Company’s thermal coal segments have experienced reduced demand as a result of sustained low natural gas pricing, reduced utilization and retirement of coal-fired power plants, the increased use of renewable energy sources, and the impact of COVID-19. The reduced demand has led to lower production levels, higher unit costs, and lower realized prices, which have contributed to operating losses at certain of the mine complexes. Further, on September 29, 2020 the U.S. District Court upheld the FTC’s decision to block the Company’s proposed joint venture. These conditions have resulted in changes to the Company’s expectations for projected future volume levels and the overall longevity of the mines. During the third quarter of 2020, the Company determined that these conditions represented indicators of impairment with respect to certain of its long-lived assets or asset groups. As a result, the Company recorded impairment charges during the three and nine months ended September 30, 2020 of million related to the Company’s equity method investment in Knight Hawk Holdings, LLC. The impairment charges were based upon estimated discounted cash flows that were based on estimates of future sales volumes, coal prices for unpriced volumes, production costs and a risk-adjusted cost of capital. These estimates generally constitute unobservable Level 3 inputs under the fair value hierarchy.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss)	9. The following items are included in accumulated other comprehensive income (loss) (“AOCI”), net of tax: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pension, ​ ​ ​ ​ ​ ​ ​ ​ ​ Postretirement ​ ​ ​ ​ Accumulated ​ ​ ​ ​ ​ and Other Post- ​ ​ ​ ​ Other ​ ​ Derivative ​ Employment ​ Available-for- ​ Comprehensive ​ ​ Instruments ​ Benefits ​ Sale Securities ​ Income (loss) ​ (In thousands) Balance at December 31, 2019 ​ $ (2,564) ​ $ 8,273 ​ $ (20) $ 5,689 Unrealized losses ​ (3,039) ​ (11,461) ​ 79 (14,421) Amounts reclassified from AOCI ​ 1,209 ​ (979) ​ (268) (37) Balance at September 30, 2020 ​ $ (4,394) ​ $ (4,166) ​ $ (209) $ (8,769) ​ The following amounts were reclassified out of AOCI: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, Line Item in the Details About AOCI Components 2020 2019 2020 2019 Statement of Operations ​ ​ (In thousands) ​ ​ ​ Coal hedges ​ $ 98 ​ $ 2,963 ​ $ 294 ​ $ 5,067 ​ Revenues Interest rate hedges ​ (638) ​ 161 ​ (1,502) ​ 1,190 ​ Interest expense ​ ​ — ​ — ​ — ​ — ​ Provision for (benefit from) income taxes ​ ​ $ (541) ​ $ 3,124 ​ $ (1,209) ​ $ 6,257 ​ Net of tax ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pension, postretirement and other post-employment benefits ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortization of actuarial gains (losses), net ​ $ (138) ​ $ 2,236 ​ $ 328 ​ $ 2,236 ​ Non-service related pension and postretirement benefit (costs) credits Amortization of prior service credits ​ ​ 30 ​ ​ — ​ ​ 84 ​ ​ — ​ ​ Non-service related pension and postretirement benefit (costs) credits Pension settlement ​ ​ 437 ​ 197 ​ ​ 567 ​ 626 ​ Non-service related pension and postretirement benefit (costs) credits ​ ​ — ​ — ​ — ​ — ​ Provision for (benefit from) income taxes ​ ​ $ 329 ​ $ 2,433 ​ $ 979 ​ $ 2,862 ​ Net of tax ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-sale securities ​ $ 128 ​ $ 35 ​ $ 268 ​ $ 50 ​ Interest and investment income ​ ​ — ​ — ​ — ​ — ​ Provision for (benefit from) income taxes ​ ​ $ 128 ​ $ 35 ​ $ 268 ​ $ 50 ​ Net of tax ​

Inventories

Inventories	9 Months Ended
	Sep. 30, 2020
Inventories
Inventories	10. Inventories consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ 2020 2019 ​ ​ (In thousands) Coal ​ $ 56,889 ​ $ 46,815 Repair parts and supplies ​ 86,507 ​ 84,083 ​ ​ $ 143,396 ​ $ 130,898 ​ The repair parts and supplies are stated net of an allowance for slow-moving and obsolete inventories of $2.5 million at September 30, 2020 and $2.2 million at December 31, 2019.

Investments in Available-for-Sa

Investments in Available-for-Sale Securities	9 Months Ended
	Sep. 30, 2020
Investments in Available-for-Sale Securities
Investments in Available-for-Sale Securities	11. The Company has invested in marketable debt securities, primarily highly liquid U.S. Treasury securities and investment grade corporate bonds. These investments are held in the custody of a major financial institution. These securities are classified as available-for-sale securities and, accordingly, the unrealized gains and losses are recorded through other comprehensive income. The Company’s investments in available-for-sale marketable securities are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ Allowance ​ ​ ​ ​ ​ ​ ​ ​ Unrealized ​ ​ for Credit ​ Fair ​ Cost Basis Gains Losses ​ ​ Losses Value ​ ​ (In thousands) Available-for-sale: ​ ​ ​ ​ ​ ​ ​ U.S. government and agency securities ​ $ 15,360 ​ $ — ​ $ (54) ​ $ — ​ $ 15,306 Corporate notes and bonds ​ 47,977 ​ 14 ​ (169) ​ — ​ 47,822 Total Investments ​ $ 63,337 ​ $ 14 ​ $ (223) ​ $ — ​ $ 63,128 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ Allowance ​ ​ ​ ​ ​ ​ ​ ​ Unrealized ​ ​ for Credit ​ Fair ​ Cost Basis Gains ​ Losses ​ ​ Losses Value ​ (In thousands) Available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. government and agency securities ​ $ 35,044 ​ $ 1 ​ $ (16) ​ $ — ​ $ 35,029 Corporate notes and bonds ​ 100,643 ​ 200 ​ (205) ​ — ​ 100,638 Total Investments ​ $ 135,687 ​ $ 201 ​ $ (221) ​ $ — ​ $ 135,667 ​ The aggregate fair value of investments with unrealized losses that were owned for less than a year was $48.5 million and $72.3 million at September 30, 2020 and December 31, 2019, respectively. The aggregate fair value of investments with unrealized losses that were owned for over a year was $9.6 million and $0.0 million at September 30, 2020 and December 31, 2019, respectively. The unrealized losses in the Company’s portfolio at September 30, 2020 are the result of normal market fluctuations. The Company does not currently intend to sell these investments before recovery of their amortized cost base. The debt securities outstanding at September 30, 2020 have maturity dates ranging from the fourth quarter of 2020 through the first quarter of 2022. The Company classifies its investments as current based on the nature of the investments and their availability to provide cash for use in current operations.

Derivatives

Derivatives	9 Months Ended
	Sep. 30, 2020
Derivatives
Derivatives	12. Interest rate risk management The Company has entered into interest rate swaps to reduce the variability of cash outflows associated with interest payments on its variable rate term loan. These swaps have been designated as cash flow hedges. For additional information on these arrangements, see Note 14, “Debt and Financing Arrangements,” in the Condensed Consolidated Financial Statements. Diesel fuel price risk management The Company is exposed to price risk with respect to diesel fuel purchased for use in its operations. The Company anticipates purchasing approximately 30 to 35 million gallons of diesel fuel for use in its operations annually. To protect the Company’s cash flows from increases in the price of diesel fuel for its operations, the Company uses forward physical diesel purchase contracts, purchased heating oil call options and New York Mercantile Exchange (“NYMEX”) gulf coast diesel swaps and options. At September 30, 2020, the Company had protected the price on the majority of its expected diesel fuel purchases for the remainder of 2020 with approximately 2 million gallons of heating oil call options with an average strike price of $1.76 per gallon and 2.0 million gallons of NYMEX gulf coast diesel swaps at an average price of approximately $1.05 per gallon. These positions are not designated as hedges for accounting purposes, and therefore, changes in the fair value are recorded immediately to earnings. Coal price risk management positions The Company may sell or purchase forward contracts, swaps and options in the over-the-counter coal market in order to manage its exposure to coal prices. The Company has exposure to the risk of fluctuating coal prices related to forecasted, index-priced sales or purchases of coal or to the risk of changes in the fair value of a fixed price physical sales contract. Certain derivative contracts may be designated as hedges of these risks. At September 30, 2020, the Company held derivatives for risk management purposes that are expected to settle in the following years: ​ ​ ​ ​ ​ ​ ​ ​ (Tons in thousands) 2020 2021 Total Coal sales 255 33 288 Coal purchases 238 — 238 ​ The Company has also entered into a minimal quantity of natural gas put options to protect the Company from decreases in natural gas prices, which could impact thermal coal demand. These options are not designated as hedges. Coal trading positions The Company may sell or purchase forward contracts, swaps and options in the over-the-counter coal market for trading purposes. The Company is exposed to the risk of changes in coal prices on the value of its coal trading portfolio. The estimated future realization of the value of the trading portfolio is $0.2 million of losses during the remainder of 2020 and $0.3 million of gains during 2021. Tabular derivatives disclosures The Company has master netting agreements with all of its counterparties which allow for the settlement of contracts in an asset position with contracts in a liability position in the event of default or termination. Such netting arrangements reduce the Company’s credit exposure related to these counterparties. For classification purposes, the Company records the net fair value of all the positions with a given counterparty as a net asset or liability in the Condensed Consolidated Balance Sheets. The amounts shown in the table below represent the fair value position of individual contracts, and not the net position presented in the accompanying Condensed Consolidated Balance Sheets. The fair value and location of derivatives reflected in the accompanying Condensed Consolidated Balance Sheets are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ ​ ​ December 31, 2019 ​ ​ Fair Value of Derivatives Asset ​ Liability ​ ​ ​ ​ Asset ​ Liability ​ ​ (In thousands) ​ Derivative ​ Derivative ​ ​ ​ ​ Derivative ​ Derivative ​ ​ ​ Derivatives Designated as Hedging Instruments ​ ​ ​ ​ ​ ​ Coal ​ $ 453 ​ $ (355) ​ ​ $ 1,351 ​ $ (962) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives Not Designated as Hedging Instruments ​ ​ ​ ​ ​ ​ Heating oil -- diesel purchases ​ 105 ​ — ​ ​ 133 ​ (112) ​ Coal -- held for trading purposes ​ 5,128 ​ (4,965) ​ ​ 18,467 ​ (18,940) ​ Coal -- risk management ​ 4,736 ​ (2,490) ​ ​ 11,662 ​ (5,856) ​ Natural gas ​ — ​ — ​ ​ 3 ​ — ​ Total ​ $ 9,969 ​ $ (7,455) ​ ​ $ 30,265 ​ $ (24,908) ​ Total derivatives ​ $ 10,422 ​ $ (7,810) ​ ​ $ 31,616 ​ $ (25,870) ​ Effect of counterparty netting ​ (7,757) ​ 7,757 ​ ​ (25,759) ​ 25,759 ​ Net derivatives as classified in the balance sheets ​ $ 2,665 ​ $ (53) ​ $ 2,612 ​ $ 5,857 ​ $ (111) ​ $ 5,746 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ ​ ​ 2020 ​ 2019 Net derivatives as reflected on the balance sheets (in thousands) ​ ​ Heating oil and coal Other current assets ​ $ 2,665 ​ $ 5,857 Coal Accrued expenses and other current liabilities ​ (53) ​ (111) ​ ​ ​ ​ $ 2,612 ​ $ 5,746 ​ The Company had a current liability representing cash collateral owed to a margin account for derivative positions primarily related to coal derivatives of $2.1 million and $4.4 million at September 30, 2020 and December 31, 2019, respectively. These amounts are not included with the derivatives presented in the table above and are included in “accrued expenses and other current liabilities” in the accompanying Condensed Consolidated Balance Sheets. The effects of derivatives on measures of financial performance are as follows: Derivatives used in Cash Flow Hedging Relationships (in thousands) Three Months Ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gain (Loss) Recognized in Other Comprehensive Income ​ Gains (Losses) Reclassified from Other Comprehensive Income into Income ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 Coal sales (1) $ (25) ​ $ 225 ​ $ (569) ​ $ 2,963 Coal purchases (2) 25 ​ (34) ​ 471 ​ — Totals ​ $ — ​ $ 191 ​ $ (98) ​ $ 2,963 ​ Derivatives Not Designated as Hedging Instruments (in thousands) Three Months Ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ Gain (Loss) Recognized ​ ​ ​ 2020 ​ ​ 2019 Coal trading — realized and unrealized (3) $ 1 ​ $ (127) Coal risk management — unrealized (3) ​ (2,650) ​ (1,417) Natural gas trading— realized and unrealized (3) ​ — ​ 14 Change in fair value of coal derivatives and coal trading activities, net total $ (2,649) ​ $ (1,530) ​ ​ ​ ​ ​ ​ ​ Coal risk management— realized (4) $ 2,593 ​ $ 3,216 Heating oil — diesel purchases (4) $ (184) ​ $ (1,670) Location in statement of operations: (1) — Revenues (2) — Cost of sales (3) — Change in fair value of coal derivatives and coal trading activities, net (4) — Other operating (income) expense, net ​ Derivatives used in Cash Flow Hedging Relationships (in thousands) Nine Months Ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gain (Loss) Recognized in Other Comprehensive Income ​ Gains (Losses) Reclassified from Other Comprehensive Income into Income ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 Coal sales (1) $ 574 ​ $ 9,472 ​ $ (1,471) ​ $ 5,750 Coal purchases (2) (570) ​ (940) ​ 1,177 ​ (686) Totals ​ $ 4 ​ $ 8,532 ​ $ (294) ​ $ 5,064 ​ Derivatives Not Designated as Hedging Instruments (in thousands) Nine Months Ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ Gain (Loss) Recognized ​ 2020 2019 Coal trading— realized and unrealized (3) $ 222 ​ $ (1,228) Coal risk management— unrealized (3) (3,561) ​ 21,145 Natural gas trading — realized and unrealized (3) 76 ​ (66) Change in fair value of coal derivatives and coal trading activities, net total ​ $ (3,263) ​ $ 19,851 ​ ​ ​ ​ ​ ​ ​ Coal risk management — realized (4) $ 6,950 ​ $ (2,076) Heating oil — diesel purchases (4) $ (889) ​ $ (2,402) ​ Location in statement of operations: (1) — Revenues (2) — Cost of sales (3) — Change in fair value of coal derivatives and coal trading activities, net (4) — Other operating (income) expense, net No ineffectiveness or amounts excluded from effectiveness testing relating to the Company’s cash flow hedging relationships were recognized in the results of operations in the three and nine month periods ended September 30, 2020 and 2019. Based on fair values at September 30, 2020, amounts on derivative contracts designated as hedge instruments in cash flow hedges to be reclassified from other comprehensive income into earnings during the next 12 months are gains of approximately $0.1 million.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	9 Months Ended
	Sep. 30, 2020
Accrued Expenses and Other Current Liabilities
Accrued Expenses and Other Current Liabilities	13. Accrued expenses and other current liabilities consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2020 ​ 2019 ​ ​ (In thousands) Payroll and employee benefits ​ $ 44,348 ​ $ 50,929 Taxes other than income taxes ​ 60,953 ​ 69,061 Interest ​ 799 ​ 133 Workers’ compensation ​ 15,282 ​ 16,119 Asset retirement obligations ​ 9,827 ​ 10,366 Other ​ 9,812 ​ 10,559 ​ ​ $ 141,021 ​ $ 157,167 ​

Debt and Financing Arrangements

Debt and Financing Arrangements	9 Months Ended
	Sep. 30, 2020
Debt and Financing Arrangements
Debt and Financing Arrangements	14. ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2020 ​ 2019 ​ (In thousands) Term loan due 2024 ($289.5 million face value) ​ $ 288,730 ​ $ 290,825 Tax Exempt Bonds ​ ​ 53,090 ​ ​ — Other ​ 59,359 ​ 25,007 Debt issuance costs ​ (6,914) ​ (5,013) ​ ​ ​ 394,265 ​ ​ 310,819 Less: current maturities of debt ​ 25,987 ​ 20,753 Long-term debt ​ $ 368,278 ​ $ 290,066 ​ Term Loan Facility In 2017, the Company entered into a senior secured term loan credit agreement (the “Credit Agreement”) in an aggregate principal amount of $300 million (the “Term Loan Debt Facility”) with Credit Suisse AG, Cayman Islands Branch, as administrative agent and collateral agent, and the other financial institutions from time to time party thereto (collectively, the “Lenders”). The Term Loan Debt Facility was issued at 99.50% of the face amount and will mature on March 7, 2024. The term loans provided under the Term Loan Debt Facility (the “Term Loans”) are subject to quarterly principal amortization payments in an amount equal to $750,000. During 2018, the Company entered into the Second Amendment (the “Second Amendment”) to its Credit Agreement. The Second Amendment reduced the interest rate on its Term Loan Debt Facility to, at the option of Arch Resources, either (i) the London interbank offered rate (“LIBOR”) plus an applicable margin of 2.75%, subject to a 1.00% LIBOR floor, or (ii) a base rate plus an applicable margin of 1.75%. The LIBOR floor remains at 1.00%. There is no change to the maturities as a result of the Second Amendment. The Term Loan Debt Facility is guaranteed by all existing and future wholly owned domestic subsidiaries of the Company (collectively, the “Subsidiary Guarantors” and, together with Arch Resources, the “Loan Parties”), subject to customary exceptions, and is secured by first priority security interests on substantially all assets of the Loan Parties, including 100% of the voting equity interests of directly owned domestic subsidiaries and 65% of the voting equity interests of directly owned foreign subsidiaries, subject to customary exceptions. The Company has the right to prepay the Term Loan at any time, and from time to time, in whole or in part without premium or penalty, upon written notice, except that any prepayment of the Term Loan that bear interest at the LIBOR Rate other than at the end of the applicable interest periods therefore shall be made with reimbursement for any funding losses and redeployment costs of the Lenders resulting therefrom. The Term Loan Debt Facility is subject to certain usual and customary mandatory prepayment events, including 100% of net cash proceeds of (i) debt issuances (other than debt permitted to be incurred under the terms of the Term Loan Debt Facility) and (ii) non-ordinary course asset sales or dispositions, subject to customary thresholds, exceptions and reinvestment rights. The Term Loan Debt Facility contains customary affirmative covenants and representations. The Term Loan Debt Facility also contains customary negative covenants, which, among other things, and subject to certain exceptions, include restrictions on (i) indebtedness, (ii) liens, (iii) liquidations, mergers, consolidations and acquisitions, (iv) disposition of assets or subsidiaries, (v) affiliate transactions, (vi) creation or ownership of certain subsidiaries, partnerships and joint ventures, (vii) continuation of or change in business, (viii) restricted payments, (ix) prepayment of subordinated and junior lien indebtedness, (x) restrictions in agreements on dividends, intercompany loans and granting liens on the collateral, (xi) loans and investments, (xii) sale and leaseback transactions, (xiii) changes in organizational documents and fiscal year and (xiv) transactions with respect to bonding subsidiaries. The Term Loan Debt Facility does not contain any financial maintenance covenants. The Term Loan Debt Facility contains customary events of default, subject to customary thresholds and exceptions, including, among other things, (i) nonpayment of principal and nonpayment of interest and fees, (ii) a material inaccuracy of a representation or warranty at the time made, (iii) a failure to comply with any covenant, subject to customary grace periods in the case of certain affirmative covenants, (iv) cross-events of default to indebtedness of at least $50 million, (v) cross-events of default to surety, reclamation or similar bonds securing obligations with an aggregate face amount of at least $50 million, (vi) uninsured judgments in excess of $50 million, (vii) any loan document shall cease to be a legal, valid and binding agreement, (viii) uninsured losses or proceedings against assets with a value in excess of $50 million, (ix) certain ERISA events, (x) a change of control or (xi) bankruptcy or insolvency proceedings relating to the Company or any material subsidiary of the Company. Accounts Receivable Securitization Facility On September 30, 2020, the Company amended and extended its existing trade accounts receivable securitization facility provided to Arch Receivable Company, LLC, a special-purpose entity that is a wholly owned subsidiary of Arch Resources (“Arch Receivable”) (the “Extended Securitization Facility”), which supports the issuance of letters of credit and requests for cash advances. The amendment to the Extended Securitization Facility reduces the size of the facility from $160 million to $110 million of borrowing capacity and extended the maturity date to September 29, 2023. Additionally, the amendment eliminated the provision that accelerated maturity upon liquidity falling below a specified level. Pursuant to the Extended Securitization Facility, Arch Receivable also agreed to a revised schedule of fees payable to the administrator and the providers of the Extended Securitization Facility. Under the Extended Securitization Facility, Arch Receivable, Arch Resources and certain of Arch Resources’s subsidiaries party to the Extended Securitization Facility have granted to the administrator of the Extended Securitization Facility a first priority security interest in eligible trade accounts receivable generated by such parties from the sale of coal and all proceeds thereof. As of September 30, 2020, letters of credit totaling $50.0 million were outstanding under the facility with $34.5 million available for borrowings. Inventory-Based Revolving Credit Facility On September 30, 2020, the Company and certain of its subsidiaries amended the senior secured inventory-based revolving credit facility in an aggregate principal amount of $50 million (the “Inventory Facility”) with Regions Bank (“Regions”) as administrative agent and collateral agent, as lender and swingline lender (in such capacities, the “Lender”) and as letter of credit issuer. Availability under the Inventory Facility is subject to a borrowing base consisting of (i) 85% of the net orderly liquidation value of eligible coal inventory, (ii) the lesser of (x) 85% of the net orderly liquidation value of eligible parts and supplies inventory and (y) 35% of the amount determined pursuant to clause (i), and (iii) 100% of Arch Resources’s Eligible Cash (defined in the Inventory Facility), subject to reduction for reserves imposed by Regions. The amendment of the Inventory Facility extended the maturity of the facility to September 29, 2023; eliminated the provision that accelerated maturity upon liquidity falling below a specified level; and reduced the minimum liquidity requirement from $175 million to $100 million. Additionally, the amendment includes provisions that reduce the advance rates for coal inventory and parts and supplies, depending on Liquidity. Revolving loan borrowings under the Inventory Facility bear interest at a per annum rate equal to, at the option of Arch Resources, either the base rate or the London interbank offered rate plus, in each case, a margin ranging from 2.50% to 3.50% (in the case of LIBOR loans) and 1.00% to 1.50% (in the case of base rate loans) determined using a Liquidity-based grid. Letters of credit under the Inventory Facility are subject to a fee in an amount equal to the applicable margin for LIBOR loans, plus customary fronting and issuance fees. All existing and future direct and indirect domestic subsidiaries of Arch Resources, subject to customary exceptions, will either constitute co-borrowers under or guarantors of the Inventory Facility (collectively with Arch Resources, the “Loan Parties”). The Inventory Facility is secured by first priority security interests in the ABL Priority Collateral (defined in the Inventory Facility) of the Loan Parties and second priority security interests in substantially all other assets of the Loan Parties, subject to customary exceptions (including an exception for the collateral that secures the Extended Securitization Facility). Arch Resources has the right to prepay borrowings under the Inventory Facility at any time and from time to time in whole or in part without premium or penalty, upon written notice, except that any prepayment of such borrowings that bear interest at the LIBOR rate other than at the end of the applicable interest periods therefore shall be made with reimbursement for any funding losses and redeployment costs of the Lender resulting therefrom. The Inventory Facility is subject to certain usual and customary mandatory prepayment events, including non-ordinary course asset sales or dispositions, subject to customary thresholds, exceptions (including exceptions for required prepayments under Arch Resources’s term loan facility) and reinvestment rights. The Inventory Facility contains certain customary affirmative and negative covenants; events of default, subject to customary thresholds and exceptions; and representations, including certain cash management and reporting requirements that are customary for asset-based credit facilities. The Inventory Facility also includes a requirement to maintain Liquidity equal to or exceeding $100 million at all times. As of September 30, 2020, letters of credit totaling $29.2 million were outstanding under the facility with $14.8 million available for borrowings. Equipment Financing On March 4, 2020, the Company entered into an equipment financing arrangement accounted for as debt. The Company received $53.6 million in exchange for conveying an interest in certain equipment in operation at its Leer Mine and entered into a master lease arrangement for that equipment. The financing arrangement contains customary terms and events of default and provides for 48 monthly payments with an average interest rate of 6.34 % maturing on March 4, 2024. Upon maturity, all interests in the subject equipment will revert back to the Company. Tax Exempt Bonds On July 2, 2020, the West Virginia Economic Development Authority (the “Issuer”) issued $53.1 million aggregate principal amount of Solid Waste Disposal Facility Revenue Bonds (Arch Resources Project), Series 2020 (the “Bonds”) pursuant to an Indenture of Trust dated as of June 1, 2020 (the “Indenture”) between the Issuer and Citibank, N.A., as trustee (the “Trustee”). The proceeds of the Bonds were loaned to the Company pursuant to a Loan Agreement dated as of June 1, 2020 between the Issuer and Arch. The Bonds are payable solely from payments to be made by the Company under the Loan Agreement as evidence by a Note from the Company to the Trustee. The proceeds of the Bonds were used to finance certain costs of the acquisition, construction, reconstruction, and equipping of solid waste disposal facilities at the Company’s Leer South development, and for capitalized interest and certain costs related to issuance of the Bonds. The Bonds will bear interest payable each January 1 and July 1, commencing January 1, 2021, at an interest rate of 5% and have a final maturity of July 1, 2045; however, the Bonds are subject to mandatory tender on July 1, 2025 at a purchase price equal to 100 % of the principal amount of the Bonds, plus accrued interest to July 1, 2025. The Bonds are subject to redemption (i) in whole or in part at any time on or after January 1, 2025 at the option of the Issuer, upon the Company’s direction at a redemption price of par, plus interest accrued to the redemption date; and (ii) at par plus interest accrued to the redemption date from certain excess Bond proceeds as further described in the Indenture. The Company’s obligations under the Loan Agreement are (i) except as otherwise described below, secured by first priority liens on and security interests in substantially all of the Company’s and Subsidiary Guarantors’ real property and other assets, subject to certain customary exceptions and permitted liens, and in any event excluding our accounts receivable and inventory; and (ii) jointly and severally guaranteed by the Subsidiary Guarantors, subject to customary exceptions. The collateral securing the Company’s obligations under the Loan Agreement is substantially the same as the collateral securing the obligations under the Term Loan Debt Facility other than with respect to variances in certain real property collateral. The real property securing the Company’s obligations under the Loan Agreement includes a subset of the real property collateral securing the obligations under the Term Loan Debt Facility and includes only mortgages on substantially all of the Company’s revenue generating metallurgical coal real property and assets, including its mining complexes at Leer, Leer South, Mountain Laurel and Beckley in West Virginia. The Company is required to provide additional mortgages in the future to secure its obligations under the Loan Agreement due to the joint venture with Peabody not consummating. The Loan Agreement contains certain affirmative covenants and representations, including but not limited to: (i) maintenance of a rating on the Bonds; (ii) maintenance of proper books of records and accounts; (iii) agreement to add additional guarantors to guarantee our obligations under the Loan Agreement in certain circumstances; (iv) procurement of customary insurance; and (v) preservation of legal existence and certain rights, franchises, licenses and permits. The Loan Agreement also contains certain customary negative covenants, which, among other things, and subject to certain exceptions, include restrictions on (i) release of collateral securing our obligations under the Loan Agreement; (ii) mergers and consolidations and disposition of assets, and (iii) restrictions on actions that may jeopardize the tax-exempt status of the Bonds. The Loan Agreement contains customary events of default, subject to customary thresholds and exceptions, including, among other things, (i) nonpayment of principal, purchase price, interest and other fees (subject to certain cure periods), (ii) bankruptcy or insolvency proceedings relating to us; (iii) material inaccuracy of a representation or warranty at the time made, (iv) cross-events of default to indebtedness of at least $50 million, (v) cross defaults to the Indenture, the guaranty related to the Bonds or any related security documents. As of September 30, 2020, Arch has received $38.1 million of the total bonds issues. The remaining $13.9 is held in trust and is recorded on the balance sheet as restricted cash. The remainder of the funds will be released as qualified expenditures are made over the next several quarters. Interest Rate Swaps The Company has entered into a series of interest rate swaps to fix a portion of the LIBOR interest rate within the term loan. The interest rate swaps qualify for cash flow hedge accounting treatment and as such, the change in the fair value of the interest rate swaps is recorded on the Company’s Condensed Consolidated Balance Sheet as an asset or liability with the effective portion of the gains or losses reported as a component of accumulated other comprehensive income and the ineffective portion reported in earnings. As interest payments are made on the term loan, amounts in accumulated other comprehensive income will be reclassified into earnings through interest expense to reflect a net interest on the term loan equal to the effective yield of the fixed rate of the swap plus 2.75% which is the spread on the revised LIBOR term loan. In the event that an interest rate swap is terminated prior to maturity, gains or losses in accumulated other comprehensive income will remain deferred and be reclassified into earnings in the periods which the hedged forecasted transaction affects earnings. Below is a summary of the Company’s outstanding interest rate swap agreements designated as hedges as of September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Notional Amount ​ ​ ​ ​ ​ ​ ​ ​ (in millions) Effective Date Fixed Rate Receive Rate Expiration Date ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 200.0 ​ June 30, 2020 2.249 % 1-month LIBOR ​ June 30, 2021 $ 100.0 ​ June 30, 2021 2.315 % 1-month LIBOR ​ June 30, 2023 ​ The fair value of the interest rate swaps at September 30, 2020 is a liability of $4.5 million, which is recorded within Other noncurrent liabilities, with the offset to accumulated other comprehensive income on the Company’s Condensed Consolidated Balance Sheet. The Company realized $0.6 million and $1.5 million of losses during the three and nine months ended September 30, 2020, respectively, related to settlements of the interest rate swaps which was recorded to interest expense on the Company’s Condensed Consolidated Statement of Operations. The interest rate swaps are classified as Level 2 within the fair value hierarchy.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2020
Income Taxes
Income Taxes	15. A reconciliation of the federal income tax provision at the statutory rate to the actual provision for (benefit from) income taxes follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2020 2019 2020 2019 ​ ​ (In thousands) Income tax provision at statutory rate ​ $ (40,128) ​ $ 22,494 ​ $ (55,922) ​ $ 51,000 Percentage depletion allowance ​ 2,242 ​ (6,347) ​ (3,358) ​ (14,111) State taxes, net of effect of federal taxes ​ (2,695) ​ 1,825 ​ (4,197) ​ 3,668 Change in valuation allowance ​ 40,734 ​ (19,120) ​ 61,115 ​ (42,925) Current expense associated with uncertain tax positions ​ ​ 226 ​ ​ 1,495 ​ ​ 3,327 ​ ​ 2,932 AMT sequestration refund ​ — ​ — ​ (1,171) ​ — Other, net ​ — ​ — ​ — ​ (56) Provision for (benefit from) income taxes ​ $ 379 ​ $ 347 ​ $ (206) ​ $ 508 ​ During the second quarter of 2020, the Company received a $37.4 million refund from the Internal Revenue Service consisting of all the remaining refundable alternative minimum tax (AMT) credits and related interest. A FIN48 reserve has been established for ​

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures Measurements
Fair Value Measurements	16. The hierarchy of fair value measurements assigns a level to fair value measurements based on the inputs used in the respective valuation techniques. The levels of the hierarchy, as defined below, give the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities and the lowest priority to unobservable inputs. ● Level 1 is defined as observable inputs such as quoted prices in active markets for identical assets. Level 1 assets include U.S. Treasury securities, and coal swaps and futures that are submitted for clearing on the New York Mercantile Exchange. ● Level 2 is defined as observable inputs other than Level 1 prices. These include quoted prices for similar assets or liabilities in an active market, quoted prices for identical assets and liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. The Company’s level 2 assets and liabilities include U.S. government agency securities, coal commodity contracts and interest rate swaps with fair values derived from quoted prices in over-the-counter markets or from prices received from direct broker quotes. ● Level 3 is defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. These include the Company’s commodity option contracts (coal, natural gas and heating oil) valued using modeling techniques, such as Black-Scholes, that require the use of inputs, particularly volatility, that are rarely observable. Changes in the unobservable inputs would not have a significant impact on the reported Level 3 fair values at September 30, 2020. The table below sets forth, by level, the Company’s financial assets and liabilities that are recorded at fair value in the accompanying Condensed Consolidated Balance Sheet: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ Total Level 1 Level 2 Level 3 ​ ​ (In thousands) Assets: ​ ​ ​ ​ Investments in marketable securities ​ $ 63,128 ​ $ 15,306 ​ $ 47,822 ​ $ — Derivatives ​ 2,665 ​ 2,560 ​ 105 ​ — Total assets ​ $ 65,793 ​ $ 17,866 ​ $ 47,927 ​ $ — Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ Derivatives ​ $ 4,545 ​ $ — ​ $ 4,545 ​ $ — ​ The Company’s contracts with its counterparties allow for the settlement of contracts in an asset position with contracts in a liability position in the event of default or termination. For classification purposes, the Company records the net fair value of all the positions with these counterparties as a net asset or liability. Each level in the table above displays the underlying contracts according to their classification in the accompanying Condensed Consolidated Balance Sheet, based on this counterparty netting. The following table summarizes the change in the fair values of financial instruments categorized as Level 3. ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Nine Months Ended ​ ​ September 30, 2020 ​ September 30, 2020 ​ ​ (In thousands) Balance, beginning of period $ 33 $ 61 Realized and unrealized losses recognized in earnings, net ​ (33) ​ (1,158) Purchases ​ — ​ 1,235 Issuances ​ — ​ (138) Settlements ​ — ​ — Ending balance ​ $ — ​ $ — ​ Net unrealized losses of $0.0 million and $0.2 million were recognized in the Condensed Consolidated Statement of Operations within Other operating income, net during the three and nine months ended September 30, 2020, respectively, related to Level 3 financial instruments held on September 30, 2020. Fair Value of Long-Term Debt At September 30, 2020 and December 31, 2019, the fair value of the Company’s debt, including amounts classified as current, was $356.7 million and $308.0 million, respectively. Fair values are based upon observed prices in an active market, when available, or from valuation models using market information, which fall into Level 2 in the fair value hierarchy.

Earnings per Common Share

Earnings per Common Share	9 Months Ended
	Sep. 30, 2020
Earnings Per Common Share
Earnings per Common Share	17. The Company computes basic net income (loss) per share using the weighted average number of common shares outstanding during the period. Diluted net income (loss) per share is computed using the weighted average number of common shares and the effect of potentially dilutive securities outstanding during the period. Potentially dilutive securities may consist of warrants, restricted stock units or other contingently issuable shares. The dilutive effect of outstanding warrants, restricted stock units and other contingently issuable shares is reflected in diluted earnings per share by application of the treasury stock method. The weighted average share impact of warrants and restricted stock units that were excluded from the calculation of diluted shares due to the Company incurring a net loss for the three and nine month periods ending September 30, 2020 were ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ ​ 2020 2019 2020 2019 ​ (In Thousands) ​ ​ ​ Weighted average shares outstanding: Basic weighted average shares outstanding 15,147 15,736 15,144 16,591 Effect of dilutive securities — 1,116 — 1,153 Diluted weighted average shares outstanding 15,147 16,852 15,144 17,744 ​ The following table provides the basis for basic and diluted earnings per share by reconciling the denominators of the computations: ​

Workers Compensation Expense

Workers Compensation Expense	9 Months Ended
	Sep. 30, 2020
Workers Compensation Expense
Workers Compensation Expense	18. The Company is liable under the Federal Mine Safety and Health Act of 1969, as subsequently amended, to provide for pneumoconiosis (occupational disease) benefits to eligible employees, former employees and dependents. The Company currently provides for federal claims principally through a self-insurance program. The Company is also liable under various state workers’ compensation statutes for occupational disease benefits. The occupational disease benefit obligation represents the present value of the actuarially computed present and future liabilities for such benefits over the employees’ applicable years of service. In October 2019, the Company filed an application with the Office of Workers’ Compensation Programs (“OWCP”) within the Department of Labor for reauthorization to self-insure federal black lung benefits. In February 2020, the Company received a reply from the OWCP confirming Arch’s status to remain self-insured contingent upon posting additional collateral of of receipt of the letter. The Company is currently appealing the ruling from the OWCP and has received an extension to self-insure during the appeal process. The Company is evaluating alternatives to self-insurance, including the purchase of commercial insurance to cover these claims. In addition, the Company is liable for workers’ compensation benefits for traumatic injuries which are calculated using actuarially-based loss rates, loss development factors and discounted based on a risk free rate. Traumatic workers’ compensation claims are insured with varying retentions/deductibles, or through state-sponsored workers’ compensation programs. Workers’ compensation expense consists of the following components: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2020 2019 2020 2019 ​ ​ (In thousands) Self-insured occupational disease benefits: ​ ​ ​ ​ Service cost ​ $ 1,892 ​ $ 1,670 ​ $ 5,674 ​ $ 5,008 Interest cost (1) ​ 1,398 ​ 1,354 ​ 4,196 ​ 4,062 Net amortization (1) ​ 297 ​ — ​ 892 ​ — Total occupational disease ​ $ 3,587 ​ $ 3,024 ​ $ 10,762 ​ $ 9,070 Traumatic injury claims and assessments ​ 2,030 ​ 2,088 ​ 6,312 ​ 6,642 Total workers’ compensation expense ​ $ 5,617 ​ $ 5,112 ​ $ 17,074 ​ $ 15,712 (1)

Employee Benefit Plans

Employee Benefit Plans	9 Months Ended
	Sep. 30, 2020
Employee Benefit Plans
Employee Benefit Plans	19. Employee Benefit Plans The following table details the components of pension benefit costs (credits): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2020 2019 2020 2019 ​ ​ (In thousands) Interest cost (1) ​ $ 1,255 ​ $ 1,922 ​ $ 4,342 ​ $ 6,439 Expected return on plan assets (1) ​ (2,022) ​ ​ (2,699) ​ ​ (6,333) ​ ​ (8,146) Pension settlement (1) ​ ​ (437) ​ (197) ​ (567) ​ (626) Amortization of prior service costs (credits) (1) ​ (27) ​ 4 ​ (83) ​ 4 Net benefit credit ​ $ (1,231) ​ $ (970) ​ $ (2,641) ​ $ (2,329) ​ The following table details the components of other postretirement benefit costs: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2020 2019 2020 2019 ​ ​ (In thousands) Service cost ​ $ 104 ​ $ 120 ​ $ 316 ​ $ 360 Interest cost (1) ​ 543 ​ 876 ​ 1,849 ​ 2,629 Amortization of other actuarial losses (gains) (1) ​ (160) ​ (2,236) ​ (1,219) ​ (2,236) Net benefit cost (credit) ​ $ 487 ​ $ (1,240) ​ $ 946 ​ $ 753 (1) In accordance with the adoption of ASU 2017-07, “Compensation-Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost,” these costs are recorded within Nonoperating expenses in the Condensed Consolidated Statement of Operations on the line item “Non-service related pension and postretirement benefit costs.”

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies
Commitments and Contingencies	20. Commitments and Contingencies The Company accrues for costs related to contingencies when a loss is probable and the amount is reasonably determinable. Disclosure of contingencies is included in the financial statements when it is at least reasonably possible that a material loss or an additional material loss in excess of amounts already accrued may be incurred. In addition, the Company is a party to numerous other claims and lawsuits with respect to various matters. The ultimate resolution of any such legal matter could result in outcomes that may be materially different from amounts the Company has accrued for such matters. The Company believes it has recorded adequate reserves for these matters.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2020
Segment Information
Segment Information	21. The Company’s reportable business segments are based on two distinct lines of business, metallurgical and thermal, and may include a number of mine complexes. The Company manages its coal sales by market, not by individual mining complex. Geology, coal transportation routes to customers, and regulatory environments also have a significant impact on the Company’s marketing and operations management. Mining operations are evaluated based on Adjusted EBITDA, per-ton cash operating costs (defined as including all mining costs except depreciation, depletion, amortization, accretion on asset retirement obligations, and pass-through transportation expenses), and on other non-financial measures, such as safety and environmental performance. Adjusted EBITDA is not a measure of financial performance in accordance with generally accepted accounting principles, and items excluded from Adjusted EBITDA are significant in understanding and assessing the Company’s financial condition. Therefore, Adjusted EBITDA should not be considered in isolation, nor as an alternative to net income (loss), income (loss) from operations, cash flows from operations or as a measure of our profitability, liquidity or performance under generally accepted accounting principles. The Company uses Adjusted EBITDA to measure the operating performance of its segments and allocate resources to the segments. Furthermore, analogous measures are used by industry analysts and investors to evaluate the Company’s operating performance. Investors should be aware that the Company’s presentation of Adjusted EBITDA may not be comparable to similarly titled measures used by other companies. The Company reports its results of operations primarily through the following reportable segments: Powder River Basin (PRB) segment containing the Company’s primary thermal operations in Wyoming; the Metallurgical (MET) segment, containing the Company’s metallurgical operations in West Virginia, and the Other Thermal segment containing the Company’s supplementary thermal operations in Colorado and Illinois. On December 13, 2019, the Company closed on its definitive agreement to sell Coal-Mac LLC, an operating mine complex within the Company’s Other Thermal coal segment. Coal-Mac is included in the Other Thermal segment results below up to the date of the divestiture. ​ Operating segment results for the three and nine months ended September 30, 2020 and 2019, are presented below. The Corporate, Other and Eliminations grouping includes these charges: idle operations; change in fair value of coal derivatives and coal trading activities, net; corporate overhead; land management activities; other support functions; and the elimination of intercompany transactions. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other ​ Other and ​ ​ ​ (In thousands) ​ PRB ​ MET ​ Thermal ​ Eliminations ​ Consolidated Three Months Ended September 30, 2020 ​ ​ ​ ​ ​ Revenues ​ $ 180,850 ​ $ 168,054 ​ $ 32,449 $ 908 ​ $ 382,261 Adjusted EBITDA ​ 34,486 ​ 12,407 ​ (2,870) ​ (26,597) ​ 17,426 Depreciation, depletion and amortization ​ 5,847 ​ 24,221 ​ 2,303 ​ 259 ​ 32,630 Accretion on asset retirement obligation ​ 3,495 ​ 486 ​ 347 ​ 619 ​ 4,947 Total assets ​ 189,942 ​ 759,202 ​ 26,766 ​ 677,427 ​ 1,653,337 Capital expenditures ​ 26 ​ 57,424 ​ 542 ​ (892) ​ 57,100 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues ​ $ 269,968 ​ $ 254,493 ​ $ 94,052 ​ $ 954 ​ $ 619,467 Adjusted EBITDA ​ 50,153 ​ 70,814 ​ 16,659 ​ (31,005) ​ 106,621 Depreciation, depletion and amortization ​ 5,956 ​ 19,962 ​ 3,852 ​ 479 ​ 30,249 Accretion on asset retirement obligation ​ 3,135 ​ 531 ​ 603 ​ 868 ​ 5,137 Total assets ​ 236,656 ​ 609,378 ​ 148,994 ​ 939,572 ​ 1,934,600 Capital expenditures ​ 5,402 ​ 36,475 ​ 6,837 ​ 738 ​ 49,452 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues ​ $ 492,406 ​ $ 489,660 ​ $ 105,481 $ 19,467 ​ $ 1,107,014 Adjusted EBITDA ​ 28,542 ​ 76,037 ​ (8,942) ​ (76,028) ​ 19,609 Depreciation, depletion and amortization ​ 16,337 ​ 69,028 ​ 6,973 ​ 1,767 ​ 94,105 Accretion on asset retirement obligation ​ 10,484 ​ 1,458 ​ 1,042 ​ 1,955 ​ 14,939 Total assets ​ 189,942 ​ 759,202 ​ 26,766 ​ 677,427 ​ 1,653,337 Capital expenditures ​ 4,268 ​ 193,586 ​ 5,113 ​ 2,694 ​ 205,661 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues ​ $ 692,845 ​ $ 769,000 ​ $ 278,235 ​ $ 4,792 ​ $ 1,744,872 Adjusted EBITDA ​ 85,433 ​ 264,284 ​ 33,699 ​ (63,977) ​ 319,439 Depreciation, depletion and amortization ​ 15,702 ​ 53,687 ​ 10,976 ​ 1,757 ​ 82,122 Accretion on asset retirement obligation ​ 9,406 ​ 1,592 ​ 1,810 ​ 2,603 ​ 15,411 Total assets ​ 236,656 ​ 609,378 ​ 148,994 ​ 939,572 ​ 1,934,600 Capital expenditures ​ 19,026 ​ 98,849 ​ 16,299 ​ 3,222 ​ 137,396 ​ A reconciliation of net income (loss) to adjusted EBITDA follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ (In thousands) ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ Net income (loss) ​ $ (191,467) ​ $ 106,769 ​ $ (266,090) ​ $ 242,350 ​ Provision for (benefit from) income taxes ​ ​ 379 ​ ​ 347 ​ ​ (206) ​ ​ 508 ​ Interest expense, net ​ 2,530 ​ 340 ​ 6,389 ​ 4,916 ​ Depreciation, depletion and amortization ​ 32,630 ​ 30,249 ​ 94,105 ​ 82,122 ​ Accretion on asset retirement obligations ​ 4,947 ​ 5,137 ​ 14,939 ​ 15,411 ​ Costs related to proposed joint venture with Peabody Energy ​ 4,423 ​ 3,754 ​ 15,938 ​ 6,772 ​ Asset impairment ​ 163,088 ​ — ​ 163,088 ​ — ​ Severance costs related to voluntary separation plan ​ 18 ​ — ​ 13,283 ​ — ​ Gain on property insurance recovery related to Mountain Laurel longwall ​ — ​ — ​ (23,518) ​ — ​ (Gain) loss on divestitures ​ ​ — ​ ​ — ​ ​ (1,369) ​ ​ 4,304 ​ Preference Rights Lease Application settlement income ​ ​ — ​ ​ (39,000) ​ ​ — ​ ​ (39,000) ​ Non-service related pension and postretirement benefit costs ​ 878 ​ (975) ​ 3,076 ​ 2,127 ​ Reorganization items, net ​ — ​ — ​ (26) ​ (71) ​ Adjusted EBITDA ​ $ 17,426 ​ $ 106,621 ​ $ 19,609 ​ $ 319,439 ​ ​

Revenue Recognition

Revenue Recognition	9 Months Ended
	Sep. 30, 2020
Revenue Recognition
Revenue Recognition	22. ASC 606-10-50-5 requires that entities disclose disaggregated revenue information in categories (such as type of good or service, geography, market, type of contract, etc.) that depict how the nature, amount, timing, and uncertainty of revenue and cash flow are affected by economic factors. ASC 606-10-55-89 explains that the extent to which an entity’s revenue is disaggregated depends on the facts and circumstances that pertain to the entity’s contracts with customers and that some entities may need to use more than one type of category to meet the objective for disaggregating revenue. In general, the Company’s business segmentation is aligned according to the nature and economic characteristics of its coal and customer relationships and provides meaningful disaggregation of each segment’s results. The Company has further disaggregated revenue between North America and Seaborne revenues which depicts the pricing and contract differences between the two. North America revenue is characterized by contracts that typically have a term of one year or longer and typically the pricing is fixed; whereas Seaborne revenue generally is derived by spot or short term contracts with pricing determined at the time of shipment or based on a market index. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other ​ Other and ​ ​ ​ ​ ​ PRB ​ MET ​ Thermal ​ Eliminations ​ Consolidated ​ (in thousands) Three Months Ended September 30, 2020 ​ ​ ​ ​ ​ North America revenues ​ $ 180,097 ​ $ 47,197 ​ $ 28,176 ​ $ 908 ​ $ 256,378 Seaborne revenues ​ 753 ​ 120,857 ​ 4,273 ​ — ​ 125,883 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total revenues ​ $ 180,850 ​ $ 168,054 ​ $ 32,449 ​ $ 908 ​ $ 382,261 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ North America revenues ​ $ 269,968 ​ $ 63,755 ​ $ 47,571 ​ $ 954 ​ $ 382,248 Seaborne revenues ​ — ​ 190,738 ​ 46,481 ​ — ​ 237,219 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total revenues ​ $ 269,968 ​ $ 254,493 ​ $ 94,052 ​ $ 954 ​ $ 619,467 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ North America revenues ​ $ 491,471 ​ $ 117,058 ​ $ 87,909 ​ $ 19,467 ​ $ 715,905 Seaborne revenues ​ 935 ​ 372,602 ​ 17,572 ​ — ​ 391,109 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total revenues ​ $ 492,406 ​ $ 489,660 ​ $ 105,481 ​ $ 19,467 ​ $ 1,107,014 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ North America revenues ​ $ 692,845 ​ $ 163,317 ​ $ 141,985 ​ $ 4,792 ​ $ 1,002,939 Seaborne revenues ​ — ​ 605,683 ​ 136,250 ​ — ​ 741,933 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total revenues ​ $ 692,845 ​ $ 769,000 ​ $ 278,235 ​ $ 4,792 ​ $ 1,744,872 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, 2020, the Company has outstanding performance obligations for the remainder of 2020 of 16.5 million tons of fixed price contracts and 1.0 million tons of variable price contracts. Additionally, the Company has outstanding performance obligations beyond 2020 of approximately 83.6 million tons of fixed price contracts and 5.0 million tons of variable price contracts. ​

Leases

Leases	9 Months Ended
	Sep. 30, 2020
Leases
Leases	23. The Company has operating and financing leases for mining equipment, office equipment, office space and transloading terminals with remaining lease terms ranging from less than one year to approximately seven years. Some of these leases include both lease and non-lease components which are accounted for as a single lease component as the Company has elected the practical expedient to combine these components for all leases. As most of the leases do not provide an implicit rate, the Company calculated the ROU assets and lease liabilities using its secured incremental borrowing rate at the lease commencement date. Information related to leases was as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, ​ ​ ​ 2020 ​ ​ 2019 Operating lease information: ​ (In thousands) Operating lease cost ​ $ 846 ​ ​ ​ $ 1,071 ​ Operating cash flows from operating leases ​ 860 ​ ​ ​ ​ 1,078 ​ Weighted average remaining lease term in years ​ 6.20 ​ ​ ​ ​ 6.19 ​ Weighted average discount rate ​ 5.5 % ​ ​ ​ 5.5 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Financing lease information: ​ ​ ​ ​ ​ ​ ​ Financing lease cost ​ $ 393 ​ ​ ​ $ — ​ Operating cash flows from financing leases ​ 303 ​ ​ ​ ​ — ​ Weighted average remaining lease term in years ​ 4.50 ​ ​ ​ ​ — ​ Weighted average discount rate ​ 6.4 % ​ ​ ​ — % ​ Future minimum lease payments under non-cancellable leases as of September 30, 2020 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating ​ ​ Finance Year ​ Leases ​ ​ Leases ​ (In thousands) 2020 ​ $ 823 ​ ​ $ 303 2021 ​ 3,367 ​ ​ 1,210 2022 ​ 3,317 ​ ​ 1,210 2023 ​ 3,285 ​ ​ 1,210 2024 ​ 3,200 ​ ​ 1,210 Thereafter ​ 7,798 ​ ​ 2,111 Total minimum lease payments ​ $ 21,790 ​ ​ $ 7,254 Less imputed interest ​ (3,485) ​ ​ (1,173) ​ ​ ​ ​ ​ ​ ​ ​ Total lease liabilities ​ $ 18,305 ​ ​ $ 6,081 ​ ​ ​ ​ ​ ​ ​ ​ As reflected on balance sheet: ​ ​ ​ ​ ​ Accrued expenses and other current liabilities ​ $ 2,427 ​ ​ $ 847 Other noncurrent liabilities ​ 15,878 ​ ​ 5,234 ​ ​ ​ ​ ​ ​ ​ ​ Total lease liability ​ $ 18,305 ​ ​ $ 6,081 ​ At September 30, 2020, the Company had an $17.6 million ROU operating lease asset finance lease asset

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2020
Basis of Presentation
Basis of Presentation	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States for interim financial reporting and U.S. Securities and Exchange Commission regulations. In the opinion of management, all adjustments, consisting of normal, recurring accruals considered necessary for a fair presentation, have been included. Results of operations for the three and nine months ended September 30, 2020 are not necessarily indicative of results to be expected for the year ending December 31, 2020. These financial statements should be read in conjunction with the audited financial statements and related notes as of and for the year ended December 31, 2019 included in the Company’s Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission. Effective May 15, 2020, Arch Coal, Inc. announced that its name changed to Arch Resources, Inc.
Recently Adopted Accounting Guidance	Recently Adopted Accounting Guidance In June 2016, the FASB issued ASU 2016-13, “Financial Instruments-Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments,” and also issued subsequent amendments to the initial guidance under ASU 2018-19, ASU 2019-04 and ASU 2019-05. The standard modifies the measurement approach for credit losses on financial instruments, including trade receivables, from an incurred loss method to a current expected credit loss method, otherwise known as “CECL.” The standard requires the measurement of expected credit losses to be based on relevant information, including historical experience, current conditions and a forecast that is supportable. The Company adopted the standard in the first quarter of 2020, with minimal impact to the Company’s financial results. As part of the adoption, the Company reviewed its portfolio of available-for-sale debt securities in an unrealized loss position, and assessed whether it intends to sell, or it is more likely than not that it will be required to sell before recovery of its amortized cost basis. The Company determined that it currently does not intend to sell these securities before recovery of their amortized cost basis. Additionally, the Company evaluated whether the decline in fair value has resulted from credit losses or other factors by considering the extent to which the fair value is less than amortized cost, any changes to the rating of the security by a rating agency, and adverse conditions specifically related to the security, among other factors. If this assessment indicates that a credit loss exists, the Company compares the present value of the cash flows expected to be collected against the amortized cost basis. A credit loss is recorded if the present value of the cash flows is less than the amortized cost basis, limited by the amount that the fair value is less than the amortized cost basis. Upon adoption, the Company did not record an allowance for credit losses on its available-for-sale debt securities. Additionally, the Company reviewed its open trade receivables arising from contractual coal sales. As part of its analysis, the Company performs periodic credit reviews of all active customers, reviews all trade receivables greater than 90 days past due, calculates historical loss rates and reviews current payment trends of all customers. ​ Recent Accounting Guidance Issued Not Yet Effective In December 2019, the FASB issued ASU 2019- 12, “Income Taxes (Topic 740) Simplifying the Accounting for Income Taxes.” ASU 2019- 12 eliminates certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. The ASU is effective for public companies for fiscal years beginning after December 15, 2020, and interim periods therein with early adoption permitted. The Company is reviewing the provisions of the standard but does not expect a significant impact to the Company's financial statements. In March 2020, the FASB issued ASU 2020-04, "Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting." The amendments provide optional guidance for a limited time to ease the potential burden in accounting for reference rate reform. The new guidance provides optional expedients and exceptions for applying U.S. GAAP to contracts, hedging relationships and other transactions affected by reference rate reform if certain criteria are met. The amendments apply only to contracts and hedging relationships that reference LIBOR or another reference rate expected to be discontinued due to reference rate reform. These amendments are effective immediately and may be applied prospectively to contract modifications made and hedging relationships entered into or evaluated on or before December 31, 2022. We are currently evaluating our contracts and the optional expedients provided by the new standard.

Asset Impairment (Tables)

Asset Impairment (Tables)	9 Months Ended
	Sep. 30, 2020
Asset Impairment
Schedule of Asset Impairment Charges [Table Text Block]	​ ​ ​ ​ ​ ​ September 30, Description 2020 ​ ​ (In thousands) Coal lands and mineral rights ​ $ 33,197 Plant and equipment ​ 43,197 Deferred development ​ ​ 50,527 Equity Investment ​ ​ 36,167 ​ ​ $ 163,088 ​ ​ ​ ​

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss)
Schedule of Accumulated Other Comprehensive Income (Loss)	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pension, ​ ​ ​ ​ ​ ​ ​ ​ ​ Postretirement ​ ​ ​ ​ Accumulated ​ ​ ​ ​ ​ and Other Post- ​ ​ ​ ​ Other ​ ​ Derivative ​ Employment ​ Available-for- ​ Comprehensive ​ ​ Instruments ​ Benefits ​ Sale Securities ​ Income (loss) ​ (In thousands) Balance at December 31, 2019 ​ $ (2,564) ​ $ 8,273 ​ $ (20) $ 5,689 Unrealized losses ​ (3,039) ​ (11,461) ​ 79 (14,421) Amounts reclassified from AOCI ​ 1,209 ​ (979) ​ (268) (37) Balance at September 30, 2020 ​ $ (4,394) ​ $ (4,166) ​ $ (209) $ (8,769)
Schedule of Comprehensive Income Reclassifications	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, Line Item in the Details About AOCI Components 2020 2019 2020 2019 Statement of Operations ​ ​ (In thousands) ​ ​ ​ Coal hedges ​ $ 98 ​ $ 2,963 ​ $ 294 ​ $ 5,067 ​ Revenues Interest rate hedges ​ (638) ​ 161 ​ (1,502) ​ 1,190 ​ Interest expense ​ ​ — ​ — ​ — ​ — ​ Provision for (benefit from) income taxes ​ ​ $ (541) ​ $ 3,124 ​ $ (1,209) ​ $ 6,257 ​ Net of tax ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pension, postretirement and other post-employment benefits ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Amortization of actuarial gains (losses), net ​ $ (138) ​ $ 2,236 ​ $ 328 ​ $ 2,236 ​ Non-service related pension and postretirement benefit (costs) credits Amortization of prior service credits ​ ​ 30 ​ ​ — ​ ​ 84 ​ ​ — ​ ​ Non-service related pension and postretirement benefit (costs) credits Pension settlement ​ ​ 437 ​ 197 ​ ​ 567 ​ 626 ​ Non-service related pension and postretirement benefit (costs) credits ​ ​ — ​ — ​ — ​ — ​ Provision for (benefit from) income taxes ​ ​ $ 329 ​ $ 2,433 ​ $ 979 ​ $ 2,862 ​ Net of tax ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-sale securities ​ $ 128 ​ $ 35 ​ $ 268 ​ $ 50 ​ Interest and investment income ​ ​ — ​ — ​ — ​ — ​ Provision for (benefit from) income taxes ​ ​ $ 128 ​ $ 35 ​ $ 268 ​ $ 50 ​ Net of tax

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Sep. 30, 2020
Inventories
Inventories	​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ 2020 2019 ​ ​ (In thousands) Coal ​ $ 56,889 ​ $ 46,815 Repair parts and supplies ​ 86,507 ​ 84,083 ​ ​ $ 143,396 ​ $ 130,898

Investments in Available-for-_2

Investments in Available-for-Sale Securities (Tables)	9 Months Ended
	Sep. 30, 2020
Investments in Available-for-Sale Securities
Available-for-sale Securities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ Allowance ​ ​ ​ ​ ​ ​ ​ ​ Unrealized ​ ​ for Credit ​ Fair ​ Cost Basis Gains Losses ​ ​ Losses Value ​ ​ (In thousands) Available-for-sale: ​ ​ ​ ​ ​ ​ ​ U.S. government and agency securities ​ $ 15,360 ​ $ — ​ $ (54) ​ $ — ​ $ 15,306 Corporate notes and bonds ​ 47,977 ​ 14 ​ (169) ​ — ​ 47,822 Total Investments ​ $ 63,337 ​ $ 14 ​ $ (223) ​ $ — ​ $ 63,128 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ Allowance ​ ​ ​ ​ ​ ​ ​ ​ Unrealized ​ ​ for Credit ​ Fair ​ Cost Basis Gains ​ Losses ​ ​ Losses Value ​ (In thousands) Available-for-sale: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. government and agency securities ​ $ 35,044 ​ $ 1 ​ $ (16) ​ $ — ​ $ 35,029 Corporate notes and bonds ​ 100,643 ​ 200 ​ (205) ​ — ​ 100,638 Total Investments ​ $ 135,687 ​ $ 201 ​ $ (221) ​ $ — ​ $ 135,667

Derivatives (Tables)

Derivatives (Tables)	9 Months Ended
	Sep. 30, 2020
Derivatives
Schedule of Price Risk Derivatives	​ ​ ​ ​ ​ ​ ​ ​ (Tons in thousands) 2020 2021 Total Coal sales 255 33 288 Coal purchases 238 — 238
Disclosure of Fair Value of Derivatives	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ ​ ​ December 31, 2019 ​ ​ Fair Value of Derivatives Asset ​ Liability ​ ​ ​ ​ Asset ​ Liability ​ ​ (In thousands) ​ Derivative ​ Derivative ​ ​ ​ ​ Derivative ​ Derivative ​ ​ ​ Derivatives Designated as Hedging Instruments ​ ​ ​ ​ ​ ​ Coal ​ $ 453 ​ $ (355) ​ ​ $ 1,351 ​ $ (962) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives Not Designated as Hedging Instruments ​ ​ ​ ​ ​ ​ Heating oil -- diesel purchases ​ 105 ​ — ​ ​ 133 ​ (112) ​ Coal -- held for trading purposes ​ 5,128 ​ (4,965) ​ ​ 18,467 ​ (18,940) ​ Coal -- risk management ​ 4,736 ​ (2,490) ​ ​ 11,662 ​ (5,856) ​ Natural gas ​ — ​ — ​ ​ 3 ​ — ​ Total ​ $ 9,969 ​ $ (7,455) ​ ​ $ 30,265 ​ $ (24,908) ​ Total derivatives ​ $ 10,422 ​ $ (7,810) ​ ​ $ 31,616 ​ $ (25,870) ​ Effect of counterparty netting ​ (7,757) ​ 7,757 ​ ​ (25,759) ​ 25,759 ​ Net derivatives as classified in the balance sheets ​ $ 2,665 ​ $ (53) ​ $ 2,612 ​ $ 5,857 ​ $ (111) ​ $ 5,746 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ ​ ​ 2020 ​ 2019 Net derivatives as reflected on the balance sheets (in thousands) ​ ​ Heating oil and coal Other current assets ​ $ 2,665 ​ $ 5,857 Coal Accrued expenses and other current liabilities ​ (53) ​ (111) ​ ​ ​ ​ $ 2,612 ​ $ 5,746
Effects of Derivatives on Measures of Financial Performance	Derivatives used in Cash Flow Hedging Relationships (in thousands) Three Months Ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gain (Loss) Recognized in Other Comprehensive Income ​ Gains (Losses) Reclassified from Other Comprehensive Income into Income ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 Coal sales (1) $ (25) ​ $ 225 ​ $ (569) ​ $ 2,963 Coal purchases (2) 25 ​ (34) ​ 471 ​ — Totals ​ $ — ​ $ 191 ​ $ (98) ​ $ 2,963 ​ Derivatives Not Designated as Hedging Instruments (in thousands) Three Months Ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ Gain (Loss) Recognized ​ ​ ​ 2020 ​ ​ 2019 Coal trading — realized and unrealized (3) $ 1 ​ $ (127) Coal risk management — unrealized (3) ​ (2,650) ​ (1,417) Natural gas trading— realized and unrealized (3) ​ — ​ 14 Change in fair value of coal derivatives and coal trading activities, net total $ (2,649) ​ $ (1,530) ​ ​ ​ ​ ​ ​ ​ Coal risk management— realized (4) $ 2,593 ​ $ 3,216 Heating oil — diesel purchases (4) $ (184) ​ $ (1,670) Location in statement of operations: (1) — Revenues (2) — Cost of sales (3) — Change in fair value of coal derivatives and coal trading activities, net (4) — Other operating (income) expense, net ​ Derivatives used in Cash Flow Hedging Relationships (in thousands) Nine Months Ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Gain (Loss) Recognized in Other Comprehensive Income ​ Gains (Losses) Reclassified from Other Comprehensive Income into Income ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 Coal sales (1) $ 574 ​ $ 9,472 ​ $ (1,471) ​ $ 5,750 Coal purchases (2) (570) ​ (940) ​ 1,177 ​ (686) Totals ​ $ 4 ​ $ 8,532 ​ $ (294) ​ $ 5,064 ​ Derivatives Not Designated as Hedging Instruments (in thousands) Nine Months Ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ Gain (Loss) Recognized ​ 2020 2019 Coal trading— realized and unrealized (3) $ 222 ​ $ (1,228) Coal risk management— unrealized (3) (3,561) ​ 21,145 Natural gas trading — realized and unrealized (3) 76 ​ (66) Change in fair value of coal derivatives and coal trading activities, net total ​ $ (3,263) ​ $ 19,851 ​ ​ ​ ​ ​ ​ ​ Coal risk management — realized (4) $ 6,950 ​ $ (2,076) Heating oil — diesel purchases (4) $ (889) ​ $ (2,402) ​ Location in statement of operations: (1) — Revenues (2) — Cost of sales (3) — Change in fair value of coal derivatives and coal trading activities, net (4) — Other operating (income) expense, net

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2020
Accrued Expenses and Other Current Liabilities
Schedule of Accrued Expenses and Other Current Liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2020 ​ 2019 ​ ​ (In thousands) Payroll and employee benefits ​ $ 44,348 ​ $ 50,929 Taxes other than income taxes ​ 60,953 ​ 69,061 Interest ​ 799 ​ 133 Workers’ compensation ​ 15,282 ​ 16,119 Asset retirement obligations ​ 9,827 ​ 10,366 Other ​ 9,812 ​ 10,559 ​ ​ $ 141,021 ​ $ 157,167

Debt and Financing Arrangemen_2

Debt and Financing Arrangements (Tables)	9 Months Ended
	Sep. 30, 2020
Debt and Financing Arrangements
Schedule of Long-term debt	​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, ​ ​ 2020 ​ 2019 ​ (In thousands) Term loan due 2024 ($289.5 million face value) ​ $ 288,730 ​ $ 290,825 Tax Exempt Bonds ​ ​ 53,090 ​ ​ — Other ​ 59,359 ​ 25,007 Debt issuance costs ​ (6,914) ​ (5,013) ​ ​ ​ 394,265 ​ ​ 310,819 Less: current maturities of debt ​ 25,987 ​ 20,753 Long-term debt ​ $ 368,278 ​ $ 290,066
Schedule of Interest Rate Derivatives	Below is a summary of the Company’s outstanding interest rate swap agreements designated as hedges as of September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Notional Amount ​ ​ ​ ​ ​ ​ ​ ​ (in millions) Effective Date Fixed Rate Receive Rate Expiration Date ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ $ 200.0 ​ June 30, 2020 2.249 % 1-month LIBOR ​ June 30, 2021 $ 100.0 ​ June 30, 2021 2.315 % 1-month LIBOR ​ June 30, 2023

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2020
Income Taxes
Schedule of Components of Income Tax Expense (Benefit)	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2020 2019 2020 2019 ​ ​ (In thousands) Income tax provision at statutory rate ​ $ (40,128) ​ $ 22,494 ​ $ (55,922) ​ $ 51,000 Percentage depletion allowance ​ 2,242 ​ (6,347) ​ (3,358) ​ (14,111) State taxes, net of effect of federal taxes ​ (2,695) ​ 1,825 ​ (4,197) ​ 3,668 Change in valuation allowance ​ 40,734 ​ (19,120) ​ 61,115 ​ (42,925) Current expense associated with uncertain tax positions ​ ​ 226 ​ ​ 1,495 ​ ​ 3,327 ​ ​ 2,932 AMT sequestration refund ​ — ​ — ​ (1,171) ​ — Other, net ​ — ​ — ​ — ​ (56) Provision for (benefit from) income taxes ​ $ 379 ​ $ 347 ​ $ (206) ​ $ 508

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures Measurements
Summary of Financial Assets and Liabilities Accounted for at Fair Value	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ Total Level 1 Level 2 Level 3 ​ ​ (In thousands) Assets: ​ ​ ​ ​ Investments in marketable securities ​ $ 63,128 ​ $ 15,306 ​ $ 47,822 ​ $ — Derivatives ​ 2,665 ​ 2,560 ​ 105 ​ — Total assets ​ $ 65,793 ​ $ 17,866 ​ $ 47,927 ​ $ — Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ Derivatives ​ $ 4,545 ​ $ — ​ $ 4,545 ​ $ —
Summary of Change in the Fair Values of Financial Instruments Categorized as Level 3	​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Nine Months Ended ​ ​ September 30, 2020 ​ September 30, 2020 ​ ​ (In thousands) Balance, beginning of period $ 33 $ 61 Realized and unrealized losses recognized in earnings, net ​ (33) ​ (1,158) Purchases ​ — ​ 1,235 Issuances ​ — ​ (138) Settlements ​ — ​ — Ending balance ​ $ — ​ $ —

Earnings per Common Share (Tabl

Earnings per Common Share (Tables)	9 Months Ended
	Sep. 30, 2020
Earnings Per Common Share
Schedule of Weighted Average Number of Shares	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ ​ 2020 2019 2020 2019 ​ (In Thousands) ​ ​ ​ Weighted average shares outstanding: Basic weighted average shares outstanding 15,147 15,736 15,144 16,591 Effect of dilutive securities — 1,116 — 1,153 Diluted weighted average shares outstanding 15,147 16,852 15,144 17,744

Workers Compensation Expense (T

Workers Compensation Expense (Tables)	9 Months Ended
	Sep. 30, 2020
Workers Compensation Expense
Workers' compensation expense	Workers’ compensation expense consists of the following components: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2020 2019 2020 2019 ​ ​ (In thousands) Self-insured occupational disease benefits: ​ ​ ​ ​ Service cost ​ $ 1,892 ​ $ 1,670 ​ $ 5,674 ​ $ 5,008 Interest cost (1) ​ 1,398 ​ 1,354 ​ 4,196 ​ 4,062 Net amortization (1) ​ 297 ​ — ​ 892 ​ — Total occupational disease ​ $ 3,587 ​ $ 3,024 ​ $ 10,762 ​ $ 9,070 Traumatic injury claims and assessments ​ 2,030 ​ 2,088 ​ 6,312 ​ 6,642 Total workers’ compensation expense ​ $ 5,617 ​ $ 5,112 ​ $ 17,074 ​ $ 15,712 (1)

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2020
Employee Benefit Plans
Schedule of Pension Benefit Costs (Credits)	The following table details the components of pension benefit costs (credits): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2020 2019 2020 2019 ​ ​ (In thousands) Interest cost (1) ​ $ 1,255 ​ $ 1,922 ​ $ 4,342 ​ $ 6,439 Expected return on plan assets (1) ​ (2,022) ​ ​ (2,699) ​ ​ (6,333) ​ ​ (8,146) Pension settlement (1) ​ ​ (437) ​ (197) ​ (567) ​ (626) Amortization of prior service costs (credits) (1) ​ (27) ​ 4 ​ (83) ​ 4 Net benefit credit ​ $ (1,231) ​ $ (970) ​ $ (2,641) ​ $ (2,329) ​ The following table details the components of other postretirement benefit costs: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ 2020 2019 2020 2019 ​ ​ (In thousands) Service cost ​ $ 104 ​ $ 120 ​ $ 316 ​ $ 360 Interest cost (1) ​ 543 ​ 876 ​ 1,849 ​ 2,629 Amortization of other actuarial losses (gains) (1) ​ (160) ​ (2,236) ​ (1,219) ​ (2,236) Net benefit cost (credit) ​ $ 487 ​ $ (1,240) ​ $ 946 ​ $ 753 (1) In accordance with the adoption of ASU 2017-07, “Compensation-Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost,” these costs are recorded within Nonoperating expenses in the Condensed Consolidated Statement of Operations on the line item “Non-service related pension and postretirement benefit costs.”

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2020
Segment Information
Schedule of Operating Segment Results	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other ​ Other and ​ ​ ​ (In thousands) ​ PRB ​ MET ​ Thermal ​ Eliminations ​ Consolidated Three Months Ended September 30, 2020 ​ ​ ​ ​ ​ Revenues ​ $ 180,850 ​ $ 168,054 ​ $ 32,449 $ 908 ​ $ 382,261 Adjusted EBITDA ​ 34,486 ​ 12,407 ​ (2,870) ​ (26,597) ​ 17,426 Depreciation, depletion and amortization ​ 5,847 ​ 24,221 ​ 2,303 ​ 259 ​ 32,630 Accretion on asset retirement obligation ​ 3,495 ​ 486 ​ 347 ​ 619 ​ 4,947 Total assets ​ 189,942 ​ 759,202 ​ 26,766 ​ 677,427 ​ 1,653,337 Capital expenditures ​ 26 ​ 57,424 ​ 542 ​ (892) ​ 57,100 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues ​ $ 269,968 ​ $ 254,493 ​ $ 94,052 ​ $ 954 ​ $ 619,467 Adjusted EBITDA ​ 50,153 ​ 70,814 ​ 16,659 ​ (31,005) ​ 106,621 Depreciation, depletion and amortization ​ 5,956 ​ 19,962 ​ 3,852 ​ 479 ​ 30,249 Accretion on asset retirement obligation ​ 3,135 ​ 531 ​ 603 ​ 868 ​ 5,137 Total assets ​ 236,656 ​ 609,378 ​ 148,994 ​ 939,572 ​ 1,934,600 Capital expenditures ​ 5,402 ​ 36,475 ​ 6,837 ​ 738 ​ 49,452 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues ​ $ 492,406 ​ $ 489,660 ​ $ 105,481 $ 19,467 ​ $ 1,107,014 Adjusted EBITDA ​ 28,542 ​ 76,037 ​ (8,942) ​ (76,028) ​ 19,609 Depreciation, depletion and amortization ​ 16,337 ​ 69,028 ​ 6,973 ​ 1,767 ​ 94,105 Accretion on asset retirement obligation ​ 10,484 ​ 1,458 ​ 1,042 ​ 1,955 ​ 14,939 Total assets ​ 189,942 ​ 759,202 ​ 26,766 ​ 677,427 ​ 1,653,337 Capital expenditures ​ 4,268 ​ 193,586 ​ 5,113 ​ 2,694 ​ 205,661 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revenues ​ $ 692,845 ​ $ 769,000 ​ $ 278,235 ​ $ 4,792 ​ $ 1,744,872 Adjusted EBITDA ​ 85,433 ​ 264,284 ​ 33,699 ​ (63,977) ​ 319,439 Depreciation, depletion and amortization ​ 15,702 ​ 53,687 ​ 10,976 ​ 1,757 ​ 82,122 Accretion on asset retirement obligation ​ 9,406 ​ 1,592 ​ 1,810 ​ 2,603 ​ 15,411 Total assets ​ 236,656 ​ 609,378 ​ 148,994 ​ 939,572 ​ 1,934,600 Capital expenditures ​ 19,026 ​ 98,849 ​ 16,299 ​ 3,222 ​ 137,396
Schedule of Reconciliation of Net Income (Loss) to Adjusted EBITDA	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ Nine Months Ended September 30, ​ (In thousands) ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ Net income (loss) ​ $ (191,467) ​ $ 106,769 ​ $ (266,090) ​ $ 242,350 ​ Provision for (benefit from) income taxes ​ ​ 379 ​ ​ 347 ​ ​ (206) ​ ​ 508 ​ Interest expense, net ​ 2,530 ​ 340 ​ 6,389 ​ 4,916 ​ Depreciation, depletion and amortization ​ 32,630 ​ 30,249 ​ 94,105 ​ 82,122 ​ Accretion on asset retirement obligations ​ 4,947 ​ 5,137 ​ 14,939 ​ 15,411 ​ Costs related to proposed joint venture with Peabody Energy ​ 4,423 ​ 3,754 ​ 15,938 ​ 6,772 ​ Asset impairment ​ 163,088 ​ — ​ 163,088 ​ — ​ Severance costs related to voluntary separation plan ​ 18 ​ — ​ 13,283 ​ — ​ Gain on property insurance recovery related to Mountain Laurel longwall ​ — ​ — ​ (23,518) ​ — ​ (Gain) loss on divestitures ​ ​ — ​ ​ — ​ ​ (1,369) ​ ​ 4,304 ​ Preference Rights Lease Application settlement income ​ ​ — ​ ​ (39,000) ​ ​ — ​ ​ (39,000) ​ Non-service related pension and postretirement benefit costs ​ 878 ​ (975) ​ 3,076 ​ 2,127 ​ Reorganization items, net ​ — ​ — ​ (26) ​ (71) ​ Adjusted EBITDA ​ $ 17,426 ​ $ 106,621 ​ $ 19,609 ​ $ 319,439 ​

Revenue Recognition (Tables)

Revenue Recognition (Tables)	9 Months Ended
	Sep. 30, 2020
Revenue Recognition
Schedule of effects of revenue recognition	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Corporate, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Other ​ Other and ​ ​ ​ ​ ​ PRB ​ MET ​ Thermal ​ Eliminations ​ Consolidated ​ (in thousands) Three Months Ended September 30, 2020 ​ ​ ​ ​ ​ North America revenues ​ $ 180,097 ​ $ 47,197 ​ $ 28,176 ​ $ 908 ​ $ 256,378 Seaborne revenues ​ 753 ​ 120,857 ​ 4,273 ​ — ​ 125,883 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total revenues ​ $ 180,850 ​ $ 168,054 ​ $ 32,449 ​ $ 908 ​ $ 382,261 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ North America revenues ​ $ 269,968 ​ $ 63,755 ​ $ 47,571 ​ $ 954 ​ $ 382,248 Seaborne revenues ​ — ​ 190,738 ​ 46,481 ​ — ​ 237,219 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total revenues ​ $ 269,968 ​ $ 254,493 ​ $ 94,052 ​ $ 954 ​ $ 619,467 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ North America revenues ​ $ 491,471 ​ $ 117,058 ​ $ 87,909 ​ $ 19,467 ​ $ 715,905 Seaborne revenues ​ 935 ​ 372,602 ​ 17,572 ​ — ​ 391,109 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total revenues ​ $ 492,406 ​ $ 489,660 ​ $ 105,481 ​ $ 19,467 ​ $ 1,107,014 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ North America revenues ​ $ 692,845 ​ $ 163,317 ​ $ 141,985 ​ $ 4,792 ​ $ 1,002,939 Seaborne revenues ​ — ​ 605,683 ​ 136,250 ​ — ​ 741,933 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total revenues ​ $ 692,845 ​ $ 769,000 ​ $ 278,235 ​ $ 4,792 ​ $ 1,744,872 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2020
Leases
Schedule of Information Related to Leases	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, ​ ​ ​ 2020 ​ ​ 2019 Operating lease information: ​ (In thousands) Operating lease cost ​ $ 846 ​ ​ ​ $ 1,071 ​ Operating cash flows from operating leases ​ 860 ​ ​ ​ ​ 1,078 ​ Weighted average remaining lease term in years ​ 6.20 ​ ​ ​ ​ 6.19 ​ Weighted average discount rate ​ 5.5 % ​ ​ ​ 5.5 % ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Financing lease information: ​ ​ ​ ​ ​ ​ ​ Financing lease cost ​ $ 393 ​ ​ ​ $ — ​ Operating cash flows from financing leases ​ 303 ​ ​ ​ ​ — ​ Weighted average remaining lease term in years ​ 4.50 ​ ​ ​ ​ — ​ Weighted average discount rate ​ 6.4 % ​ ​ ​ — %
Schedule of Future Minimum Lease Payments	Future minimum lease payments under non-cancellable leases as of September 30, 2020 were as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ Operating ​ ​ Finance Year ​ Leases ​ ​ Leases ​ (In thousands) 2020 ​ $ 823 ​ ​ $ 303 2021 ​ 3,367 ​ ​ 1,210 2022 ​ 3,317 ​ ​ 1,210 2023 ​ 3,285 ​ ​ 1,210 2024 ​ 3,200 ​ ​ 1,210 Thereafter ​ 7,798 ​ ​ 2,111 Total minimum lease payments ​ $ 21,790 ​ ​ $ 7,254 Less imputed interest ​ (3,485) ​ ​ (1,173) ​ ​ ​ ​ ​ ​ ​ ​ Total lease liabilities ​ $ 18,305 ​ ​ $ 6,081 ​ ​ ​ ​ ​ ​ ​ ​ As reflected on balance sheet: ​ ​ ​ ​ ​ Accrued expenses and other current liabilities ​ $ 2,427 ​ ​ $ 847 Other noncurrent liabilities ​ 15,878 ​ ​ 5,234 ​ ​ ​ ​ ​ ​ ​ ​ Total lease liability ​ $ 18,305 ​ ​ $ 6,081

Joint Venture with Peabody En_2

Joint Venture with Peabody Energy (Details) - Implementation Agreement - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 18, 2019
Schedule of Equity Method Investments [Line Items]
Economic interest held					33.50%
Incurred expenses related to regulatory approval process	$ 4.4	$ 3.8	$ 15.9	$ 6.8
Peabody Energy Corporation
Schedule of Equity Method Investments [Line Items]
Economic interest held					66.50%

Gain on Property Insurance Re_2

Gain on Property Insurance Recovery Related to Mountain Laurel Longwall (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020USD ($)	Jun. 30, 2020item
Business Interruption Loss [Line Items]
Gain on Business Interruption Insurance Recovery | $	$ 23,518
Longwall system's not recoverable | item		123
Mountain Laurel Longwall Operations
Business Interruption Loss [Line Items]
Gain on Business Interruption Insurance Recovery | $	$ 23,500
Hydraulic Shields not recoverable | item		176

Severance Costs Related To Vo_2

Severance Costs Related To Voluntary Separation Plan (Details) $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended
	Sep. 30, 2020USD ($)	Jun. 30, 2020employee	Sep. 30, 2020USD ($)
Severance Costs Related To Voluntary Separation Plan
Severance Costs | $	$ 18		$ 13,283
Number of corporate staff accepted voluntary separation package		53
Number of Employees accepted voluntary separation package		201

Divestitures (Details)

Divestitures (Details)	Sep. 14, 2017USD ($)company	Jun. 30, 2020USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
(Gain) loss on divestitures			$ (1,369,000)	$ 4,304,000
Charge for bankruptcy claims				4,300,000
Lone Mountain Processing LLC | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of mining companies | company	2
(Gain) loss on divestitures	$ (21,300,000)
Dal-Tex and Briar Branch Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
(Gain) loss on divestitures			$ (1,369,000)	$ 4,304,000
Dal-Tex and Briar Branch Properties | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Divestiture of Interest in Subsidiaries and Affiliates, Total		$ 0
Gain on disposal		$ 1,400,000

Preference Rights Lease Appli_2

Preference Rights Lease Application Settlement Income (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended
	Oct. 31, 2019	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Gain Contingencies [Line Items]
Gain related to settlement				$ 39,000	$ 23,518	$ 39,000
Preference Rights Lease Application (PRLA)
Gain Contingencies [Line Items]
Gain related to settlement			$ 8,700	39,000	25,800
Royalty credits to be received due to settlement		$ 5,000		$ 67,000
Royalty credits to be received due to settlement, percentage of royalty obligations				50.00%
One-time payment for ownership interest	$ 27,000
Payment to acquire investment, closing fees	$ 1,000
Receivable			$ 27,800		$ 27,800
Minimum | Preference Rights Lease Application (PRLA)
Gain Contingencies [Line Items]
Royalty credits to be received due to settlement, period of recognition		18 months
Maximum | Preference Rights Lease Application (PRLA)
Gain Contingencies [Line Items]
Royalty credits to be received due to settlement, period of recognition		24 months

Asset Impairment (Details)

Asset Impairment (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Coal lands and mineral rights	$ 33,197
Plant and equipment	43,197
Deferred development	50,527
Equity investment	36,167
Asset impairment charges	163,088	$ 163,088
Knight Hawk
Equity investment	36,200
PRB | Coal Creek Mine
Asset impairment charges	51,800
Other Thermal | Viper Mine
Asset impairment charges	33,500
Other Thermal | West Elk Mine
Asset impairment charges	$ 41,600

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020USD ($)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 640,536
Unrealized gains	(14,421)
Amounts reclassified from AOCI	(37)
Ending Balance	365,646
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	5,689
Ending Balance	(8,769)
Derivative instruments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(2,564)
Unrealized gains	(3,039)
Amounts reclassified from AOCI	1,209
Ending Balance	(4,394)
Pension, postretirement and other post-employment benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	8,273
Unrealized gains	(11,461)
Amounts reclassified from AOCI	(979)
Ending Balance	(4,166)
Available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(20)
Unrealized gains	79
Amounts reclassified from AOCI	(268)
Ending Balance	$ (209)

Accumulated Other Comprehensi_4

Accumulated Other Comprehensive Income (Schedule of Reclassifications) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Revenues	$ 382,261	$ 619,467	$ 1,107,014	$ 1,744,872
Interest expense	(2,989)	(4,049)	(9,900)	(12,856)
Provision for (benefit from) income taxes	(379)	(347)	206	(508)
Interest and investment income	459	3,709	3,511	7,940
Net income (loss)	(191,467)	106,769	(266,090)	242,350
Reclassification out of Accumulated Other Comprehensive Income | Derivative instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Revenues	98	2,963	294	5,067
Interest expense	(638)	161	(1,502)	1,190
Provision for (benefit from) income taxes	0	0	0	0
Net income (loss)	(541)	3,124	(1,209)	6,257
Reclassification out of Accumulated Other Comprehensive Income | Pension, postretirement and other post-employment benefits
Accumulated Other Comprehensive Income (Loss) [Line Items]
Provision for (benefit from) income taxes	0	0	0	0
Amortization of actuarial gains (losses), net	(138)	2,236	328	2,236
Amortization of prior service credits	30		84
Pension settlement	437	197	567	626
Net income (loss)	329	2,433	979	2,862
Reclassification out of Accumulated Other Comprehensive Income | Available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Provision for (benefit from) income taxes	0	0	0	0
Interest and investment income	128	35	268	50
Net income (loss)	$ 128	$ 35	$ 268	$ 50

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Inventories
Coal	$ 56,889	$ 46,815
Repair parts and supplies	86,507	84,083
Inventories	143,396	130,898
Allowance for slow-moving and obsolete inventories	$ 2,500	$ 2,200

Investments in Available-for-_3

Investments in Available-for-Sale Securities (Schedule of Investments) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, Cost Basis	$ 63,337	$ 135,687
Available-for-sale, Gains	14	201
Available-for-sale, Losses	(223)	(221)
Available-for-sale, Fair Value	63,128	135,667
Available-for-sale, Short-Term Investments	63,128	135,667
U.S. government and agency securities
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, Cost Basis	15,360	35,044
Available-for-sale, Gains		1
Available-for-sale, Losses	(54)	(16)
Available-for-sale, Fair Value	15,306	35,029
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Available-for-sale, Cost Basis	47,977	100,643
Available-for-sale, Gains	14	200
Available-for-sale, Losses	(169)	(205)
Available-for-sale, Fair Value	$ 47,822	$ 100,638

Investments in Available-for-_4

Investments in Available-for-Sale Securities (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Investments in Available-for-Sale Securities
Unrealized losses owned for less than 12 months	$ 48.5	$ 72.3
Unrealized losses owed for over a year	$ 9.6	$ 0

Derivatives (Narrative) (Detail

Derivatives (Narrative) (Details) gal in Millions, $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2020USD ($)	Sep. 30, 2020USD ($)$ / Optiongal	Dec. 31, 2021USD ($)	Dec. 31, 2019USD ($)
Derivative [Line Items]
Value of trading portfolio realized - gains (losses) | $	$ (0.2)
Current asset representing cash collateral posted | $		$ 2.1		$ 4.4
Derivative contracts expected to be reclassified from OCI into earnings | $		$ 0.1
Not Designated as Hedging Instrument | Heating Oil
Derivative [Line Items]
Quantities under derivative contracts (in gallons) | gal		2
Derivative, average price risk option strike price (in used per gallon) | $ / Option		1.76
Not Designated as Hedging Instrument | Diesel Purchases | Minimum
Derivative [Line Items]
Diesel fuel purchased annually (in gallons) | gal		30
Not Designated as Hedging Instrument | Diesel Purchases | Maximum
Derivative [Line Items]
Diesel fuel purchased annually (in gallons) | gal		35
Forecast
Derivative [Line Items]
Value of trading portfolio realized - gains (losses) | $			$ 0.3
NYMEX | Not Designated as Hedging Instrument | Diesel Purchases
Derivative [Line Items]
Quantities under derivative contracts (in gallons) | gal		2
Derivative, average price risk option strike price (in used per gallon) | $ / Option		1.05

Derivatives (Schedule of Price

Derivatives (Schedule of Price Risk Derivatives) (Details) T in Thousands	9 Months Ended
	Sep. 30, 2020T
Coal sales
Derivative [Line Items]
Derivatives held (in tons)	288
Coal purchases
Derivative [Line Items]
Derivatives held (in tons)	238
2020 | Coal sales
Derivative [Line Items]
Derivatives held (in tons)	255
2020 | Coal purchases
Derivative [Line Items]
Derivatives held (in tons)	238
2021 | Coal sales
Derivative [Line Items]
Derivatives held (in tons)	33

Derivatives (Disclosure Of Fair

Derivatives (Disclosure Of Fair Value Of Derivatives) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative Assets	$ 10,422	$ 31,616
Derivative Liabilities	(7,810)	(25,870)
Effect of counterparty netting in derivative assets	(7,757)	(25,759)
Effect of counterparty netting in derivative liabilities	7,757	25,759
Derivative Asset	2,665	5,857
Derivative Liability	(53)	(111)
Net derivatives as classified in the balance sheets	2,612	5,746
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	9,969	30,265
Derivative Liabilities	(7,455)	(24,908)
Not Designated as Hedging Instrument | Coal Contract
Derivative [Line Items]
Derivative Assets	5,128	18,467
Derivative Liabilities	(4,965)	(18,940)
Coal Contract | Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	453	1,351
Derivative Liabilities	(355)	(962)
Coal Contract | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	4,736	11,662
Derivative Liabilities	(2,490)	(5,856)
Heating oil - diesel purchases | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	105	133
Derivative Liabilities		(112)
Natural gas | Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Assets	0	3
Derivative Liabilities	$ 0	$ 0

Derivatives (Net Derivatives As

Derivatives (Net Derivatives As Reflected On The Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ 2,612	$ 5,746
Accrued expenses and other current liabilities
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	(53)	(111)
Heating oil and coal | Other current assets
Derivatives, Fair Value [Line Items]
Net derivatives as classified in the balance sheet	$ 2,665	$ 5,857

Derivatives (Effects Of Derivat

Derivatives (Effects Of Derivatives On Measures Of Financial Performance) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of coal derivatives and coal trading activities, net	$ (2,649)	$ (1,530)	$ (3,263)	$ 19,851
Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income		191	4	8,532
Gains (Losses) Reclassified from Other Comprehensive Income into Income	(98)	2,963	(294)	5,064
Designated as Hedging Instrument | Coal sales | Coal Contract | Coal sales
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income	(25)	225	574	9,472
Gains (Losses) Reclassified from Other Comprehensive Income into Income	(569)	2,963	(1,471)	5,750
Designated as Hedging Instrument | Coal purchases | Coal Contract | Coal purchases
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income	25	(34)	(570)	(940)
Gains (Losses) Reclassified from Other Comprehensive Income into Income	471	0	1,177	(686)
Not Designated as Hedging Instrument | Coal Contract | Coal and natural gas realized and unrealized
Derivative Instruments, Gain (Loss) [Line Items]
Realized and Unrealized Gain (Loss) on Derivatives	1	(127)	222	(1,228)
Unrealized Gain (Loss) on Derivatives	(2,650)	(1,417)	(3,561)	21,145
Not Designated as Hedging Instrument | Coal Contract | Other operating (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives	2,593	3,216	6,950	(2,076)
Not Designated as Hedging Instrument | Natural gas | Coal and natural gas realized and unrealized
Derivative Instruments, Gain (Loss) [Line Items]
Realized and Unrealized Gain (Loss) on Derivatives		14	76	(66)
Not Designated as Hedging Instrument | Heating oil - diesel purchases | Other operating (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Heating oil realized and unrealized gains and losses	$ (184)	$ (1,670)	$ (889)	$ (2,402)

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accrued Expenses and Other Current Liabilities
Payroll and employee benefits	$ 44,348	$ 50,929
Taxes other than income taxes	60,953	69,061
Interest	799	133
Workers' compensation	15,282	16,119
Asset retirement obligations	9,827	10,366
Other	9,812	10,559
Accrued expenses and other current liabilities	$ 141,021	$ 157,167

Debt and Financing Arrangemen_3

Debt and Financing Arrangements (Long term Debt) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jul. 02, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Debt issuance costs	$ (6,914)		$ (5,013)
Total	394,265		310,819
Less: current maturities of debt	25,987		20,753
Long-term debt	368,278		290,066
Term loan due 2024
Debt Instrument [Line Items]
Long-term debt	288,730		290,825
Debt instrument, face amount	289,500
Tax Exempt Bonds
Debt Instrument [Line Items]
Long-term debt	53,090
Debt instrument, face amount		$ 53,100
Other Debt
Debt Instrument [Line Items]
Long-term debt	$ 59,359		$ 25,007

Debt and Financing Arrangemen_4

Debt and Financing Arrangements (Narrative) (Details)	Jul. 02, 2020USD ($)	Mar. 04, 2020USD ($)installment	Mar. 07, 2017USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2018	Dec. 31, 2017USD ($)	Aug. 31, 2020USD ($)	Jun. 30, 2020USD ($)	Dec. 31, 2019USD ($)
Line of Credit Facility [Line Items]
Restricted cash				$ 13,919,000	$ 13,919,000
Additional availability for borrowings					14,800,000
Fair value of derivative assets				10,422,000	10,422,000					$ 31,616,000
Interest Rate Swap
Line of Credit Facility [Line Items]
Fair value of derivative assets				(4,500,000)	(4,500,000)
Interest rate swaps settlements gains				600,000	1,500,000
Equipment financing arrangement
Line of Credit Facility [Line Items]
Interest rate		6.34%
Tax Exempt Bonds
Line of Credit Facility [Line Items]
Debt instrument, face amount	$ 53,100,000
Interest rate	5.00%
Mandatory tender percentage	100.00%
Proceeds from issuance of debt				38,100,000
Restricted cash				13,900,000	$ 13,900,000
Tax Exempt Bonds | Minimum
Line of Credit Facility [Line Items]
Covenant for cross-events of default to indebtedness				50,000,000
Senior Notes | New Term Loan Debt Facility
Line of Credit Facility [Line Items]
Net cash proceeds of from debt issuances and other non-ordinary sales or dispositions (percent)			100
Default to indebtedness			$ 50,000,000
Default to surety, reclamation or similar bond			50,000,000
Default to uninsured judgment			50,000,000
Uninsured losses or proceedings against			50,000,000
Senior Notes | New Term Loan Debt Facility | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate						2.75%
Senior Notes | New Term Loan Debt Facility | LIBOR | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate						1.00%
Secured Debt | Equipment financing arrangement
Line of Credit Facility [Line Items]
Debt instrument, face amount		$ 53,600,000
Number of monthly payments | installment		48
Line of Credit | New Term Loan Debt Facility | Base Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate						1.75%
New Term Loan Debt Facility | Senior Notes
Line of Credit Facility [Line Items]
Debt instrument, face amount			$ 300,000,000
Percentage of face amount			99.50
Quarterly amortization payments			$ 750,000
Amount of voting equity interests of domestic subsidiaries guaranteed (percent)			100
Amount of voting equity interests of foreign owned subsidiaries guaranteed (percent)			65
New Term Loan Debt Facility | Senior Notes | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate					2.75%
Line of Credit | Secured Debt
Line of Credit Facility [Line Items]
Letters of credit outstanding				50,000,000	$ 50,000,000
Line of Credit | Secured Debt | Regions Bank
Line of Credit Facility [Line Items]
Covenant minimum amount							$ 100,000,000
Letters of credit outstanding				29,200,000	29,200,000
Current borrowing capacity				110,000,000	110,000,000				$ 160,000,000
Line of Credit | Secured Debt | Accounts Receivable Securitization Facility | Arch Receivable Company, LLC
Line of Credit Facility [Line Items]
Current borrowing capacity				34,500,000	$ 34,500,000
Line of Credit | Secured Debt | Inventory-Based Revolving Credit Facility | Regions Bank
Line of Credit Facility [Line Items]
Debt instrument, face amount							$ 50,000,000
Percentage of coal inventory borrowing base							85
Percentage of parts and supplies inventory borrowing base							85
Percentage of clause borrowing base							35
Percent of eligible cash							100.00%
Line of Credit | Secured Debt | Inventory-Based Revolving Credit Facility | LIBOR | Regions Bank | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate					2.50%
Line of Credit | Secured Debt | Inventory-Based Revolving Credit Facility | LIBOR | Regions Bank | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate					3.50%
Line of Credit | Secured Debt | Inventory-Based Revolving Credit Facility | Base Rate | Regions Bank | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate					1.00%
Line of Credit | Secured Debt | Inventory-Based Revolving Credit Facility | Base Rate | Regions Bank | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate					1.50%
Line of Credit | Line of Credit | Inventory-Based Revolving Credit Facility | Regions Bank
Line of Credit Facility [Line Items]
Covenant minimum amount				$ 100,000,000	$ 100,000,000			$ 175,000,000

Debt and Financing Arrangemen_5

Debt and Financing Arrangements (Interest rate derivatives) (Details) $ in Millions	Sep. 30, 2020USD ($)
June 30, 2020
Debt Instrument [Line Items]
Notional Amount	$ 200
Fixed Rate	2.249%
June 30, 2021
Debt Instrument [Line Items]
Notional Amount	$ 100
Fixed Rate	2.315%

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020
Income Taxes
Income tax provision at statutory rate	$ (40,128)	$ 22,494	$ (55,922)	$ 51,000
Percentage depletion allowance	2,242	(6,347)	(3,358)	(14,111)
State taxes, net of effect of federal taxes	(2,695)	1,825	(4,197)	3,668
Change in valuation allowance	40,734	(19,120)	61,115	(42,925)
Current expense associated with uncertain tax positions	226	1,495	3,327	2,932
AMT sequestration refund			(1,171)
Other, net			0	(56)
Provision for (benefit from) income taxes	379	$ 347	(206)	$ 508
Refund, AMT credits					$ 37,400
Tax reserve for portion of refund subject to audit	$ 13,300		$ 13,300
Percentage of the total income tax refund amount subject to audit	40.00%

Fair Value Measurements (Summar

Fair Value Measurements (Summary Of Financial Assets And Liabilities Accounted For At Fair Value) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets:
Investments in marketable securities	$ 63,128	$ 135,667
Derivatives	2,665
Total assets	65,793
Liabilities:
Derivatives	4,545
Level 1
Assets:
Investments in marketable securities	15,306
Derivatives	2,560
Total assets	17,866
Liabilities:
Derivatives	0
Level 2
Assets:
Investments in marketable securities	47,822
Derivatives	105
Total assets	47,927
Liabilities:
Derivatives	4,545
Level 3
Assets:
Investments in marketable securities	0
Derivatives	0
Total assets	0
Liabilities:
Derivatives	$ 0

Fair Value Measurements (Summ_2

Fair Value Measurements (Summary Of Change In The Fair Values Of Financial Instruments Categorized As Level 3) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 33	$ 61
Realized and unrealized gains recognized in earnings, net	$ (33)	(1,158)
Purchases		1,235
Issuances		$ (138)

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of debt, including amounts classified as current	$ 356.7	$ 356.7	$ 308
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net unrealized losses related to level 3 financial instruments	$ 0	$ (0.2)

Earnings per Common Share (Deta

Earnings per Common Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Weighted average shares outstanding:
Basic weighted average shares outstanding (in shares)	15,147,000	15,736,000	15,144,000	16,591,000
Effect of dilutive securities (in shares)		1,116,000		1,153,000
Diluted weighted average shares outstanding (in shares)	15,147,000	16,852,000	15,144,000	17,744,000
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities excluded	178,333
Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities excluded			169,555

Workers Compensation Expense (D

Workers Compensation Expense (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 29, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accrued Workers Compensation [Line Items]
Additional collateral amount	$ 71,100
Number of days required to submit additional collateral to retain self-insurance status	30 days
Occupational disease
Accrued Workers Compensation [Line Items]
Service cost		$ 1,892	$ 1,670	$ 5,674	$ 5,008
Interest cost		1,398	1,354	4,196	4,062
Net amortization(1)		297	0	892	0
Net benefit credit		3,587	3,024	10,762	9,070
Traumatic injury claims and assessments
Accrued Workers Compensation [Line Items]
Traumatic injury claims and assessments		2,030	2,088	6,312	6,642
Total workers' compensation expense
Accrued Workers Compensation [Line Items]
Total workers' compensation expense		$ 5,617	$ 5,112	$ 17,074	$ 15,712

Employee Benefit Plans (Details

Employee Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined benefit pension plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 1,255	$ 1,922	$ 4,342	$ 6,439
Expected return on plan assets	(2,022)	(2,699)	(6,333)	(8,146)
Pension settlement	(437)	(197)	(567)	(626)
Amortization of prior service costs (credits)	(27)	4	(83)	4
Net benefit credit	(1,231)	(970)	(2,641)	(2,329)
Other postretirement benefits plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	104	120	316	360
Interest cost	543	876	1,849	2,629
Amortization of other actuarial losses (gains)	(160)	(2,236)	(1,219)	(2,236)
Net benefit credit	$ 487	$ (1,240)	$ 946	$ 753

Segment Information (Schedule O

Segment Information (Schedule Of Operating Segment Results) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)segment	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			2
Revenues	$ 382,261	$ 619,467	$ 1,107,014	$ 1,744,872
Adjusted EBITDA	17,426	106,621	19,609	319,439
Depreciation, depletion and amortization	32,630	30,249	94,105	82,122
Accretion on asset retirement obligations	4,947	5,137	14,939	15,411
Total assets	1,653,337	1,934,600	1,653,337	1,934,600	$ 1,867,756
Capital expenditures	57,100	49,452	205,661	137,396
Operating Segments | PRB
Segment Reporting Information [Line Items]
Revenues	180,850	269,968	492,406	692,845
Adjusted EBITDA	34,486	50,153	28,542	85,433
Depreciation, depletion and amortization	5,847	5,956	16,337	15,702
Accretion on asset retirement obligations	3,495	3,135	10,484	9,406
Total assets	189,942	236,656	189,942	236,656
Capital expenditures	26	5,402	4,268	19,026
Operating Segments | MET
Segment Reporting Information [Line Items]
Revenues	168,054	254,493	489,660	769,000
Adjusted EBITDA	12,407	70,814	76,037	264,284
Depreciation, depletion and amortization	24,221	19,962	69,028	53,687
Accretion on asset retirement obligations	486	531	1,458	1,592
Total assets	759,202	609,378	759,202	609,378
Capital expenditures	57,424	36,475	193,586	98,849
Operating Segments | Other Thermal
Segment Reporting Information [Line Items]
Revenues	32,449	94,052	105,481	278,235
Adjusted EBITDA	(2,870)	16,659	(8,942)	33,699
Depreciation, depletion and amortization	2,303	3,852	6,973	10,976
Accretion on asset retirement obligations	347	603	1,042	1,810
Total assets	26,766	148,994	26,766	148,994
Capital expenditures	542	6,837	5,113	16,299
Corporate, Other and Eliminations
Segment Reporting Information [Line Items]
Revenues	908	954	19,467	4,792
Adjusted EBITDA	(26,597)	(31,005)	(76,028)	(63,977)
Depreciation, depletion and amortization	259	479	1,767	1,757
Accretion on asset retirement obligations	619	868	1,955	2,603
Total assets	677,427	939,572	677,427	939,572
Capital expenditures	$ (892)	$ 738	$ 2,694	$ 3,222

Segment Information (Reconcilia

Segment Information (Reconciliation Segment Income To Consolidated Income Before Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Net income (loss)	$ (191,467)	$ 106,769	$ (266,090)	$ 242,350
Provision for (benefit from) income taxes	379	347	(206)	508
Interest expense, net	2,530	340	6,389	4,916
Depreciation, depletion and amortization	32,630	30,249	94,105	82,122
Accretion on asset retirement obligations	4,947	5,137	14,939	15,411
Costs related to proposed joint venture with Peabody Energy	4,423	3,754	15,938	6,772
Asset impairment	163,088		163,088
Severance costs related to voluntary separation plan	18		13,283
Gain on property insurance recovery related to Mountain Laurel longwall		39,000	23,518	39,000
(Gain) loss on divestitures			(1,369)	4,304
Preference Rights Lease Application settlement income		(39,000)	(23,518)	(39,000)
Non-service related pension and postretirement benefit costs	878	(975)	3,076	2,127
Reorganization items, net			(26)	(71)
Adjusted EBITDA	$ 17,426	$ 106,621	19,609	319,439
Dal-Tex and Briar Branch Properties
Segment Reporting Information [Line Items]
(Gain) loss on divestitures			$ (1,369)	$ 4,304

Revenue Recognition (Disaggrega

Revenue Recognition (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 382,261	$ 619,467	$ 1,107,014	$ 1,744,872
Corporate, Other and Eliminations
Disaggregation of Revenue [Line Items]
Revenues	908	954	19,467	4,792
North America revenues
Disaggregation of Revenue [Line Items]
Revenues	256,378	382,248	715,905	1,002,939
North America revenues | Corporate, Other and Eliminations
Disaggregation of Revenue [Line Items]
Revenues	908	954	19,467	4,792
Seaborne revenues
Disaggregation of Revenue [Line Items]
Revenues	125,883	237,219	391,109	741,933
Seaborne revenues | Corporate, Other and Eliminations
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
PRB | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	180,850	269,968	492,406	692,845
PRB | North America revenues | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	180,097	269,968	491,471	692,845
PRB | Seaborne revenues | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	753	0	935	0
MET | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	168,054	254,493	489,660	769,000
MET | North America revenues | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	47,197	63,755	117,058	163,317
MET | Seaborne revenues | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	120,857	190,738	372,602	605,683
Other Thermal | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	32,449	94,052	105,481	278,235
Other Thermal | North America revenues | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	28,176	47,571	87,909	141,985
Other Thermal | Seaborne revenues | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	$ 4,273	$ 46,481	$ 17,572	$ 136,250

Revenue Recognition (Narrative)

Revenue Recognition (Narrative) (Details) T in Millions	Sep. 30, 2020T
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations, fixed price contracts (in tons)	16.5
Remaining performance obligations, variable price contracts (in tons)	1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligations, fixed price contracts (in tons)	83.6
Remaining performance obligations, variable price contracts (in tons)	5

Leases (Narrative) (Details)

Leases (Narrative) (Details) $ in Millions	Sep. 30, 2020USD ($)
Lessee, Lease, Description [Line Items]
Right-of-use operating lease asset	$ 17.6
Finance Lease, Right-of-Use Asset	$ 5.9
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other Assets, Noncurrent
Minimum
Lessee, Lease, Description [Line Items]
Operating lease, remaining lease terms	1 year
Maximum
Lessee, Lease, Description [Line Items]
Operating lease, remaining lease terms	7 years

Leases (Information Related to

Leases (Information Related to Leases) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Lease information:
Operating lease cost	$ 846	$ 1,071
Operating cash flows from operating leases	$ 860	$ 1,078
Weighted average remaining lease term in years	6 years 2 months 12 days	6 years 2 months 8 days
Weighted average discount rate	5.50%	5.50%
Financing lease cost	$ 393
Operating cash flows from financing leases	$ 303
Weighted average remaining lease term in years	4 years 6 months	0 years
Weighted average discount rate	6.40%

Leases (Future Minimum Lease Pa

Leases (Future Minimum Lease Payments) (Details) $ in Thousands	Sep. 30, 2020USD ($)
Operating Leases
2020	$ 823
2021	3,367
2022	3,317
2023	3,285
2024	3,200
Thereafter	7,798
Total minimum lease payments	21,790
Less imputed interest	(3,485)
Total operating lease liability	18,305
As reflected on balance sheet:
Accrued expenses and other current liabilities	2,427
Other noncurrent liabilities	15,878
Total operating lease liability	18,305
Finance Leases
2020	303
2021	1,210
2022	1,210
2023	1,210
2024	1,210
Thereafter	2,111
Total minimum lease payments	7,254
Less imputed interest	(1,173)
Total finance lease liability	6,081
As reflected on balance sheet:
Accrued expenses and other current liabilities	847
Other noncurrent liabilities	5,234
Finance Lease, Liability	6,081
Right-of-use operating lease asset	$ 17,600
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other Assets, Noncurrent
Right-of-use finance lease asset	$ 5,900
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other Assets, Noncurrent