Condensed Consolidated Income Statements - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Condensed Consolidated Income Statements
Revenues	$ 594,412	$ 382,261	$ 1,402,345	$ 1,107,014
Costs, expenses and other operating
Cost of sales (exclusive of items shown separately below)	423,826	345,539	1,089,061	1,036,886
Depreciation, depletion and amortization	30,760	32,630	84,441	94,105
Accretion on asset retirement obligations	5,437	4,947	16,311	14,939
Change in fair value of coal derivatives and coal trading activities, net	19,641	2,649	28,931	3,263
Selling, general and administrative expenses	21,081	21,541	66,679	64,024
Costs related to proposed joint venture with Peabody Energy		4,423		15,938
Asset impairment and restructuring		163,106		176,371
Gain on property insurance recovery related to Mountain Laurel longwall				(23,518)
Gain on divestitures				(1,369)
Other operating income, net	(1,731)	(4,894)	(11,344)	(16,768)
Costs, expenses and other operating	499,014	569,941	1,274,079	1,363,871
Income (loss) from operations	95,398	(187,680)	128,266	(256,857)
Interest expense, net
Interest expense	(6,151)	(2,989)	(13,220)	(9,900)
Interest and investment income		459	474	3,511
Interest expense, net	(6,151)	(2,530)	(12,746)	(6,389)
Income (loss) before nonoperating expenses	89,247	(190,210)	115,520	(263,246)
Nonoperating (expenses) income
Non-service related pension and postretirement benefit costs	(1,186)	(878)	(3,252)	(3,076)
Reorganization items, net				26
Nonoperating (expenses) income	(1,186)	(878)	(3,252)	(3,050)
Income (loss) before income taxes	88,061	(191,088)	112,268	(266,296)
Provision for (benefit from) income taxes	(1,082)	379	1,301	(206)
Net income (loss)	$ 89,143	$ (191,467)	$ 110,967	$ (266,090)
Net income (loss) per common share
Basic earnings (loss) per share (in dollars per share)	$ 5.83	$ (12.64)	$ 7.26	$ (17.57)
Diluted earnings (loss) per share (in dollars per share)	$ 4.92	$ (12.64)	$ 6.49	$ (17.57)
Weighted average shares outstanding
Basic weighted average shares outstanding (in shares)	15,302	15,147	15,293	15,144
Diluted weighted average shares outstanding (in shares)	18,105	15,147	17,101	15,144
Dividends declared per common share (in dollars per share)				$ 0.50