Segment Information - Reconciliation segment income to net income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Segment Information
Net Income (Loss)	$ 55,953	$ 198,108
Provision for income taxes	3,719	37,138
Interest expense, net	(1,784)	790
Depreciation, depletion and amortization	38,820	35,479
Accretion on asset retirement obligation	5,869	5,292
Non-service related pension and postretirement benefit costs (credits)	286	(592)
Net loss resulting from early retirement of debt		1,126
Adjusted EBITDA	102,863	277,341
EBITDA from idled or otherwise disposed operations	3,697	4,032
Selling, general and administrative expenses	25,587	26,022
Other	(1,681)	1,917
Segment Adjusted EBITDA from coal operations	$ 130,466	$ 309,312