Revenue From Contracts With Customers - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	$ 1,084,278	$ 1,017,406
Coal
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	1,070,347	1,009,255
Power Generation
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	447,469	434,728
Industrial
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	277,480	202,065
Metallurgical
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	345,398	372,462
Third-Party Terminal Revenue
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	8,502	4,956
Other Revenue
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	5,429	3,195
Domestic | Coal
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	442,511	390,812
Domestic | Power Generation
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	377,920	341,809
Domestic | Industrial
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	25,180	25,499
Domestic | Metallurgical
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	39,411	23,504
Export | Coal
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	627,836	618,443
Export | Power Generation
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	69,549	92,919
Export | Industrial
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	252,300	176,566
Export | Metallurgical
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	$ 305,987	$ 348,958