Revenue From Contracts With Customers - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	$ 4,164,775	$ 2,164,406	$ 2,506,635
Coal
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	4,129,481	2,117,634	2,458,735
Power Generation
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	1,860,427	906,121	1,072,015
Industrial
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	940,168	752,617	999,990
Metallurgical
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	1,328,886	458,896	386,730
Third-Party Terminal Revenue
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	21,477	31,064	47,900
Other Revenue
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	13,817	15,708
Domestic | Coal
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	1,821,320	713,728	717,633
Domestic | Power Generation
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	1,531,509	649,056	672,509
Domestic | Industrial
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	132,628	19,811	34,453
Domestic | Metallurgical
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	157,183	44,861	10,671
Export | Coal
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	2,308,161	1,403,906	1,741,102
Export | Power Generation
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	328,918	257,065	399,506
Export | Industrial
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	807,540	732,806	965,537
Export | Metallurgical
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	$ 1,171,703	$ 414,035	$ 376,059