Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities
Net income	$ 464,038	$ 1,330,914	$ 337,573
Adjustments to reconcile to cash from operating activities:
Depreciation, depletion and amortization	146,418	133,300	120,327
Accretion on asset retirement obligations	21,170	17,721	21,748
Deferred income taxes	87,091	(222,023)	8
Employee stock-based compensation expense	25,443	27,383	20,539
Amortization relating to financing activities	1,751	2,459	6,549
(Gain) loss on disposals and divestitures, net	(731)	(997)	23,276
Reclamation work completed	(21,456)	(13,720)	(39,047)
Contribution to fund for asset retirement obligations	(6,273)	(115,993)	(20,000)
Changes in:
Receivables	(31,763)	77,274	(212,950)
Inventories	(21,246)	(66,281)	(30,726)
Accounts payable, accrued expenses and other current liabilities	(31,323)	84,947	45,547
Income taxes, net	(938)	(30,507)	1,820
Coal derivative assets and liabilities, including margin account	1,572	1,274	(3,553)
Asset retirement obligations	3,441	(1,193)	(13,697)
Pension, postretirement and other postemployment benefits	(10,434)	(25,537)	4,571
Other	8,614	10,519	(23,701)
Cash provided by operating activities	635,374	1,209,540	238,284
Investing activities
Capital expenditures	(176,037)	(172,728)	(245,440)
Minimum royalty payments	(1,175)	(1,069)	(1,186)
Proceeds from disposals and divestitures	4,055	1,972	21,228
Purchases of short-term investments	(35,412)	(39,731)
Proceeds from sales of short-term investments	40,292	17,337	87,486
Investments in and advances to affiliates, net	(17,345)	(9,575)	(3,303)
Cash used in investing activities	(185,622)	(203,794)	(141,215)
Financing activities
Payments on term loan due 2024	(3,000)	(273,788)	(7,895)
Proceeds from equipment financing			19,438
Proceeds from tax exempt bonds			44,985
Payments on convertible debt	(58,430)	(208,130)
Net payments on other debt	(18,943)	(11,235)	(11,195)
Debt financing costs	(0)	(1,035)	(2,057)
Purchases of treasury stock	(125,508)	(156,790)
Dividends paid	(206,125)	(456,392)	(3,830)
Payments for taxes related to net share settlement of equity awards	(30,240)	(7,052)	(4,840)
Proceeds from warrants exercised	44,242	19,540	1,175
Cash (used in) provided by financing activities	(398,004)	(1,094,882)	35,781
Increase (decrease) in cash and cash equivalents, including restricted cash	51,748	(89,136)	132,850
Cash and cash equivalents, including restricted cash, beginning of period	237,159	326,295	193,445
Cash and cash equivalents, including restricted cash, end of period	288,907	237,159	326,295
SUPPLEMENTAL CASH FLOW INFORMATION
Cash and cash equivalents	287,807	236,059	325,194
Restricted Cash	1,100	1,100	1,101
Cash paid during the period for interest	$ 10,466	$ 18,820	$ 31,568