Segment Information - Reconciliation segment income to net income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Segment Information
Net income	$ 198,108	$ 271,872
Provision for income taxes	37,138	455
Interest expense, net	790	7,023
Depreciation, depletion and amortization	35,479	32,210
Accretion on asset retirement obligation	5,292	4,430
Non-service related pension and postretirement benefit (credits) costs	(592)	873
Net loss resulting from early retirement of debt	1,126	4,120
Adjusted EBITDA	277,341	320,983
EBITDA from idled or otherwise disposed operations	4,032	2,390
Selling, general and administrative expenses	26,022	26,648
Other	1,917	9,482
Segment Adjusted EBITDA from coal operations	$ 309,312	$ 359,503