Other Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Other Liabilities Disclosure [Abstract]
Subsidence Liability	$ 118,191	$ 88,259
Accrued Compensation and Benefits	57,563	54,138
Accrued Other Taxes	50,759	6,973
Other	67,594	31,928
Current Portion of Long-Term Liabilities:
Asset Retirement Obligations	41,496	35,554
Pneumoconiosis Benefits	25,259	16,389
Postretirement Benefits Other than Pensions	21,422	17,887
Workers' Compensation	17,360	11,056
Total Other Accrued Liabilities	$ 399,644	$ 262,184