CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 269,386	$ 268,207
Trade accounts receivable, net of allowance for credit losses of $217 and $234 as of March 31, 2024 and December 31, 2023, respectively	526,222	509,682
Inventories, net	246,033	231,344
Prepaid expenses and other current assets	34,868	39,064
Total current assets	1,076,509	1,048,297
Property, plant, and equipment, net of accumulated depreciation and amortization of $588,735 and $558,905 as of March 31, 2024 and December 31, 2023, respectively	607,637	588,992
Owned and leased mineral rights, net of accumulated depletion and amortization of $106,429 and $99,826 as of March 31, 2024 and December 31, 2023, respectively	449,892	451,160
Other acquired intangibles, net of accumulated amortization of $40,218 and $38,543 as of March 31, 2024 and December 31, 2023, respectively	44,904	46,579
Long-term restricted investments	38,055	40,597
Long-term restricted cash	121,927	115,918
Deferred income taxes	8,284	8,028
Other non-current assets	113,601	106,486
Total assets	2,460,809	2,406,057
Current liabilities:
Current portion of long-term debt	3,392	3,582
Trade accounts payable	151,453	128,836
Accrued expenses and other current liabilities	186,444	177,512
Total current liabilities	341,289	309,930
Long-term debt	6,034	6,792
Workers’ compensation and black lung obligations	186,023	189,226
Pension obligations	101,800	101,908
Asset retirement obligations	172,758	166,509
Deferred income taxes	41,226	39,142
Other non-current liabilities	20,535	18,622
Total liabilities	869,665	832,129
Commitments and Contingencies (Note 14)
Stockholders’ Equity
Preferred stock - par value $0.01, 5,000,000 shares authorized, none issued	0	0
Common stock - par value $0.01, 50,000,000 shares authorized, 22,371,165 issued and 13,007,215 outstanding at March 31, 2024 and 22,058,135 issued and 12,938,679 outstanding at December 31, 2023	224	221
Additional paid-in capital	830,536	834,482
Accumulated other comprehensive loss	(39,837)	(40,587)
Treasury stock, at cost: 9,363,950 shares at March 31, 2024 and 9,119,456 shares at December 31, 2023	(1,295,639)	(1,189,715)
Retained earnings	2,095,860	1,969,527
Total stockholders’ equity	1,591,144	1,573,928
Total liabilities and stockholders’ equity	$ 2,460,809	$ 2,406,057