Segment Information (Reconciliation Segment Income To Net Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Information
Net income (loss)	$ 271,872	$ (6,042)
Provision for income taxes	455	378
Interest expense, net	7,023	3,800
Depreciation, depletion and amortization	32,210	25,797
Accretion on asset retirement obligations	4,430	5,437
Non-service related pension and postretirement benefit costs	873	1,527
Net loss resulting from early retirement of debt	4,120
Adjusted EBITDA	320,983	30,897
EBITDA from idled or otherwise disposed operations	2,390	3,566
Selling, general and administrative expenses	26,648	21,480
Other	9,482	(1,265)
Segment Adjusted EBITDA from coal operations	$ 359,503	$ 54,678