Condensed Consolidated Income Statements - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Condensed Consolidated Income Statements
Revenues	$ 744,601	$ 863,835	$ 2,371,826	$ 2,865,129
Costs, expenses and other operating
Cost of sales (exclusive of items shown separately below)	596,889	610,027	1,774,753	1,758,012
Depreciation, depletion and amortization	36,717	33,958	108,273	98,948
Accretion on asset retirement obligations	5,292	4,430	15,877	13,290
Change in fair value of coal derivatives, net	(46)	(12,252)	1,361	5,144
Selling, general and administrative expenses	24,279	26,107	73,092	79,271
Other operating (income) expense, net	(2,812)	16,997	(11,398)	18,796
Costs, expenses and other operating	660,319	679,267	1,961,958	1,973,461
Income from operations	84,282	184,568	409,868	891,668
Interest income (expense), net
Interest expense	(3,120)	(4,060)	(10,783)	(16,245)
Interest and investment income	4,803	2,224	12,340	2,776
Interest income (expense), net	1,683	(1,836)	1,557	(13,469)
Income before nonoperating expenses	85,965	182,732	411,425	878,199
Nonoperating expense
Non-service related pension and postretirement benefit credits (costs)	4,507	(857)	5,692	(2,189)
Net loss resulting from early retirement of debt		(394)	(1,126)	(14,143)
Nonoperating expenses	4,507	(1,251)	4,566	(16,332)
Income before income taxes	90,472	181,481	415,991	861,867
Provision for income taxes	16,781	474	66,839	1,424
Net income	$ 73,691	$ 181,007	$ 349,152	$ 860,443
Net income per common share
Basic earnings per share (in dollars per share)	$ 4.05	$ 9.84	$ 19.20	$ 50.97
Diluted earnings per share (in dollars per share)	$ 3.91	$ 8.68	$ 18.12	$ 41.00
Weighted average shares outstanding
Basic weighted average shares outstanding (in shares)	18,187	18,396	18,189	16,881
Diluted weighted average shares outstanding (in shares)	18,840	20,908	19,270	21,210
Dividends declared per common share (in dollars per share)	$ 3.97	$ 6.00	$ 9.53	$ 14.36