Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Property, Plant and Equipment [Line Items]
Total Property, Plant and Equipment	$ 8,556,680	$ 5,764,081
Less: Accumulated Depreciation, Depletion and Amortization	4,081,726	3,842,382
Total Property, Plant and Equipment - Net	4,474,954	1,921,699
Plant and Equipment
Property, Plant and Equipment [Line Items]
Total Property, Plant and Equipment	4,746,089	3,633,741
Coal Properties and Surface Lands
Property, Plant and Equipment [Line Items]
Total Property, Plant and Equipment	2,223,908	913,819
Airshafts
Property, Plant and Equipment [Line Items]
Total Property, Plant and Equipment	580,174	521,334
Mine Development
Property, Plant and Equipment [Line Items]
Total Property, Plant and Equipment	669,306	366,260
Advance Mining Royalties
Property, Plant and Equipment [Line Items]
Total Property, Plant and Equipment	$ 337,203	$ 328,927