Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($)	Dec. 31, 2022	Dec. 31, 2021
Deferred Tax Asset:
Postretirement benefits other than pensions	$ 56,119,000	$ 84,130,000
Asset retirement obligations	44,680,000	47,180,000
Pneumoconiosis benefits	33,946,000	47,681,000
Compensation	8,826,000	5,203,000
Workers' compensation	7,099,000	11,419,000
State bonus, net of Federal	2,973,000	4,219,000
Long-term disability	1,463,000	1,931,000
Financing	838,000	0
Net operating loss	211,000	937,000
Operating lease liability	46,000	135,000
Other	4,957,000	5,772,000
Total Deferred Tax Asset	161,158,000	208,607,000
Valuation Allowance	0	(937,000)
Net Deferred Tax Asset	161,158,000	207,670,000
Deferred Tax Liability:
Equity Partnerships	(118,231,000)	(99,811,000)
Property, plant and equipment	(54,322,000)	(40,064,000)
Advance mining royalties	(6,782,000)	(7,270,000)
Salary retirement	(3,737,000)	(2,739,000)
Financing	0	(640,000)
Right of use assets	0	(135,000)
Total Deferred Tax Liability	(183,072,000)	(150,659,000)
Net Deferred Tax (Liability) Asset	$ (21,914,000)
Net Deferred Tax (Liability) Asset		$ 57,011,000