Other Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Other Liabilities Disclosure [Abstract]
Subsidence Liability	$ 105,671	$ 105,322
Accrued Compensation and Benefits	40,208	73,763
Accrued Income Taxes	15,557	0
Accrued Other Taxes	12,742	12,276
Deferred Revenue	7,071	9,517
Accrued Interest	3,120	6,283
Other	8,195	10,457
Current Portion of Long-Term Liabilities:
Asset Retirement Obligations	28,571	28,571
Postretirement Benefits Other than Pensions	19,297	19,327
Pneumoconiosis Benefits	14,880	15,071
Workers' Compensation	9,666	10,019
Total Other Accrued Liabilities	$ 264,978	$ 290,606