Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Consolidated Statements of Operations
Revenues	$ 3,724,593	$ 2,208,042	$ 1,467,592
Costs, expenses and other operating
Cost of sales (exclusive of items shown separately below)	2,338,863	1,579,836	1,378,479
Depreciation, depletion and amortization	133,300	120,327	121,552
Accretion on asset retirement obligations	17,721	21,748	19,887
Change in fair value of coal derivatives and coal trading activities, net	1,274	(2,392)	5,219
Selling, general and administrative expenses	105,355	92,342	82,397
Costs related to proposed joint venture with Peabody Energy			16,087
Asset impairment and restructuring			221,380
Gain on property insurance recovery related to Mountain Laurel longwall			(23,518)
Loss (Gain) on divestitures		24,225	(1,505)
Other operating expense (income), net	18,669	4,826	(22,246)
Costs, expenses and other operating	2,615,182	1,840,912	1,797,732
Income (loss) from operations	1,109,411	367,130	(330,140)
Interest expense, net
Interest expense	(20,461)	(23,972)	(14,432)
Interest and investment income	7,299	628	3,808
Interest expense, net	(13,162)	(23,344)	(10,624)
Income (loss) before nonoperating expenses	1,096,249	343,786	(340,764)
Nonoperating (expenses) income
Non-service related pension and postretirement benefit costs	(2,841)	(4,339)	(3,884)
Net loss resulting from early retirement of debt	(14,420)
Reorganization items, net			26
Nonoperating expenses	(17,261)	(4,339)	(3,858)
Income (loss) before income taxes	1,078,988	339,447	(344,622)
(Benefit from) provision for income taxes	(251,926)	1,874	(7)
Net income (loss)	$ 1,330,914	$ 337,573	$ (344,615)
Earnings per common share
Basic earnings per share (in dollars per share)	$ 77.67	$ 22.04	$ (22.74)
Diluted earnings per share (in dollars per share)	$ 63.88	$ 19.20	$ (22.74)
Weighted average shares outstanding
Basic weighted average shares outstanding (in shares)	17,136	15,318	15,153
Diluted weighted average shares outstanding (in shares)	20,985	17,579	15,153
Dividends declared per common share (in dollars per share)	$ 25.11	$ 0.25