CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues:
Coal revenues	$ 410,614	$ 653,828	$ 878,981	$ 1,260,788
Other revenues	1,224	2,378	3,317	4,532
Total revenues	411,838	656,206	882,298	1,265,320
Costs and expenses:
Cost of coal sales (exclusive of items shown separately below)	383,279	496,746	781,139	1,012,440
Depreciation, depletion and amortization	49,262	62,814	103,727	124,085
Accretion on asset retirement obligations	7,304	6,847	14,679	13,079
Amortization of acquired intangibles, net	2,096	(343)	2,961	(7,026)
Asset impairment and restructuring	184,173	5,826	217,882	5,826
Selling, general and administrative expenses (exclusive of depreciation, depletion and amortization shown separately above)	12,028	14,783	27,509	35,734
Merger-related costs	0	156	0	987
Total other operating (income) loss:
Mark-to-market adjustment for acquisition-related obligations	(2,052)	1,014	(17,049)	2,950
Other (income) expense	(124)	1,414	(704)	(7,485)
Total costs and expenses	635,966	589,257	1,130,144	1,180,590
(Loss) income from operations	(224,128)	66,949	(247,846)	84,730
Other income (expense):
Interest expense	(18,814)	(16,077)	(36,419)	(31,232)
Interest income	5,533	1,885	6,511	3,821
Loss on modification and extinguishment of debt	0	(26,459)	0	(26,459)
Equity loss in affiliates	(1,047)	(2,475)	(1,790)	(2,959)
Miscellaneous loss, net	188	(523)	(720)	(1,389)
Total other expense, net	(14,140)	(43,649)	(32,418)	(58,218)
(Loss) income from continuing operations before income taxes	(238,268)	23,300	(280,264)	26,512
Income tax (expense) benefit	(33)	1,000	2,155	5,778
Net (loss) income from continuing operations	(238,301)	24,300	(278,109)	32,290
Discontinued operations:
Loss from discontinued operations before income taxes	0	(163,867)	0	(165,457)
Income tax benefit from discontinued operations	0	25,906	0	26,321
Loss from discontinued operations	0	(137,961)	0	(139,136)
Net loss	$ (238,301)	$ (113,661)	$ (278,109)	$ (106,846)
Basic loss per common share:
(Loss) income from continuing operations (in dollars per share)	$ (13.02)	$ 1.27	$ (15.22)	$ 1.70
Loss from discontinued operations (in dollars per share)	0	(7.21)	0	(7.32)
Net loss (in dollars per share)	(13.02)	(5.94)	(15.22)	(5.62)
Diluted loss per common share:
(Loss) income from continuing operations (in dollars per share)	(13.02)	1.25	(15.22)	1.66
Loss from discontinuing operations (in dollars per share)	0	(7.10)	0	(7.14)
Net loss (in dollars per share)	$ (13.02)	$ (5.85)	$ (15.22)	$ (5.48)
Weighted average shares - basic (in shares)	18,304,853	19,123,705	18,275,382	19,009,643
Weighted average shares - diluted (in shares)	18,304,853	19,420,471	18,275,382	19,480,183
Revenue from Contract with Customer, Product and Service [Extensible List]	us-gaap:PublicUtilitiesInventoryCoalMember	us-gaap:PublicUtilitiesInventoryCoalMember	us-gaap:PublicUtilitiesInventoryCoalMember	us-gaap:PublicUtilitiesInventoryCoalMember