Components of Coal Workers' Pneumoconiosis (CWP) and Workers' Compensation Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
CWP
Defined Contribution Plan Disclosure [Line Items]
Service Cost	$ 1,990	$ 747	$ 3,806	$ 1,493
Interest Cost	3,670	2,066	7,089	4,132
Amortization of Actuarial Loss (Gain)	43	108	85	217
State Administrative Fees and Insurance Bond Premiums	0	0	0	0
Net Periodic Benefit Cost	5,703	2,921	10,980	5,842
Workers' Compensation
Defined Contribution Plan Disclosure [Line Items]
Service Cost	1,728	1,464	3,456	2,928
Interest Cost	555	572	1,110	1,145
Amortization of Actuarial Loss (Gain)	(460)	(540)	(920)	(1,080)
State Administrative Fees and Insurance Bond Premiums	2,374	465	4,110	929
Net Periodic Benefit Cost	$ 4,197	$ 1,961	$ 7,756	$ 3,922