Condensed Consolidated Income Statements - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Condensed Consolidated Income Statements
Revenues	$ 757,294	$ 1,133,358	$ 1,627,225	$ 2,001,294
Costs, expenses and other operating
Cost of sales (exclusive of items shown separately below)	606,127	639,760	1,177,864	1,147,985
Depreciation, depletion and amortization	36,077	32,780	71,556	64,990
Accretion on asset retirement obligations	5,293	4,430	10,585	8,860
Change in fair value of coal derivatives, net	2,869	1,877	1,407	17,396
Selling, general and administrative expenses	22,791	26,516	48,813	53,164
Other operating (income) expense, net	(4,879)	5,238	(8,586)	1,799
Costs, expenses and other operating	668,278	710,601	1,301,639	1,294,194
Income from operations	89,016	422,757	325,586	707,100
Interest income (expense), net
Interest expense	(3,537)	(5,138)	(7,663)	(12,185)
Interest and investment income	4,201	528	7,537	552
Interest income (expense), net	664	(4,610)	(126)	(11,633)
Income before nonoperating expenses	89,680	418,147	325,460	695,467
Nonoperating expense
Non-service related pension and postretirement benefit credits (costs)	593	(459)	1,185	(1,332)
Net loss resulting from early retirement of debt		(9,629)	(1,126)	(13,749)
Nonoperating expenses	593	(10,088)	59	(15,081)
Income before income taxes	90,273	408,059	325,519	680,386
Provision for income taxes	12,920	496	50,058	951
Net income	$ 77,353	$ 407,563	$ 275,461	$ 679,435
Net income per common share
Basic earnings per share (in dollars per share)	$ 4.20	$ 24.26	$ 15.16	$ 42.14
Diluted earnings per share (in dollars per share)	$ 4.04	$ 19.30	$ 14.16	$ 32.21
Weighted average shares outstanding
Basic weighted average shares outstanding (in shares)	18,406	16,801	18,165	16,124
Diluted weighted average shares outstanding (in shares)	19,135	21,452	19,459	21,362
Dividends declared per common share (in dollars per share)	$ 2.45	$ 8.11	$ 5.56	$ 8.36