Consolidated Income Statements - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Consolidated Income Statements
Revenues	$ 3,145,843	$ 3,724,593	$ 2,208,042
Costs, expenses and other operating
Cost of sales (exclusive of items shown separately below)	2,341,956	2,338,863	1,579,836
Depreciation, depletion and amortization	146,418	133,300	120,327
Accretion on asset retirement obligations	21,170	17,721	21,748
Change in fair value of coal derivatives, net	1,572	1,274	(2,392)
Selling, general and administrative expenses	98,871	105,355	92,342
Loss on divestitures			24,225
Other operating (income) expense, net	(10,598)	18,669	4,826
Costs, expenses and other operating	2,599,389	2,615,182	1,840,912
Income from operations	546,454	1,109,411	367,130
Interest income (expense), net
Interest expense	(14,821)	(20,461)	(23,972)
Interest and investment income	17,259	7,299	628
Interest income (expense), net	2,438	(13,162)	(23,344)
Income before nonoperating expenses	548,892	1,096,249	343,786
Nonoperating expense
Non-service related pension and postretirement benefit credits (costs)	3,786	(2,841)	(4,339)
Net loss resulting from early retirement of debt	(1,126)	(14,420)
Nonoperating expenses	2,660	(17,261)	(4,339)
Income before income taxes	551,552	1,078,988	339,447
Provision for (benefit from) income taxes	87,514	(251,926)	1,874
Net income	$ 464,038	$ 1,330,914	$ 337,573
Net income per common share
Basic earnings per share (in dollars per share)	$ 25.45	$ 77.67	$ 22.04
Diluted earnings per share (in dollars per share)	$ 24.20	$ 63.88	$ 19.20
Weighted average shares outstanding
Basic weighted average shares outstanding (in shares)	18,233	17,136	15,318
Diluted weighted average shares outstanding (in shares)	19,183	20,985	17,579
Dividends declared per common share (in dollars per share)	$ 10.66	$ 25.11