Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets
Cash and cash equivalents	$ 236,059	$ 325,194
Short-term investments	36,993	14,463
Restricted cash	1,100	1,101
Trade accounts receivable (net of $0 allowance at December 31, 2022 and December 31, 2021)	236,999	324,304
Other receivables	18,301	8,271
Inventories	223,015	156,734
Other current assets	71,384	52,804
Total current assets	823,851	882,871
Property, plant and equipment, net
Coal lands and mineral rights	406,085	406,822
Plant and equipment	968,420	844,107
Deferred mine development	475,037	402,470
Property, plant and equipment, gross	1,849,542	1,653,399
Less accumulated depreciation, depletion and amortization	(662,514)	(533,356)
Property, plant and equipment, net	1,187,028	1,120,043
Other assets
Deferred income taxes	209,470
Equity investments	17,267	15,403
Fund for asset retirement obligations	135,993	20,000
Other noncurrent assets	59,499	78,843
Total other assets	422,229	114,246
Total assets	2,433,108	2,117,160
Current Liabilities
Accounts payable	211,848	131,986
Accrued expenses and other current liabilities	157,043	167,304
Current maturities of debt	57,988	223,050
Total current liabilities	426,879	522,340
Long-term debt	116,288	337,623
Asset retirement obligations	235,736	192,672
Accrued pension benefits	1,101	1,300
Accrued postretirement benefits other than pension	49,674	73,565
Accrued workers' compensation	155,756	224,105
Other noncurrent liabilities	82,094	81,689
Total liabilities	1,067,528	1,433,294
Stockholders' equity
Common stock, $0.01 par value, authorized 300,000 shares, issued 28,761 and 25,481 shares at December 31, 2022 and December 31, 2021, respectively	288	255
Paid-in capital	724,660	784,356
Retained earnings	1,565,374	712,478
Treasury stock, 11,207 and 10,088 shares at December 31, 2022 and December 31, 2021, respectively, at cost	(986,171)	(827,381)
Accumulated other comprehensive income	61,429	14,158
Total stockholders' equity	1,365,580	683,866
Total liabilities and stockholders' equity	$ 2,433,108	$ 2,117,160