Revenue From Contracts With Customers - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	$ 1,141,014	$ 1,102,361	$ 2,225,292	$ 2,119,767
Coal
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	1,126,679	1,093,366	2,197,026	2,102,621
Power Generation
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	401,042	475,612	848,511	910,340
Industrial
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	366,720	273,545	644,200	475,610
Metallurgical
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	358,917	344,209	704,315	716,671
Third-Party Terminal Revenue
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	9,942	4,540	18,444	9,496
Other Revenue
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	4,393	4,455	9,822	7,650
Domestic \| Coal
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	389,911	499,359	832,422	890,171
Domestic \| Power Generation
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	324,515	414,634	702,435	756,443
Domestic \| Industrial
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	26,535	40,671	51,715	66,170
Domestic \| Metallurgical
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	38,861	44,054	78,272	67,558
Export \| Coal
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	736,768	594,007	1,364,604	1,212,450
Export \| Power Generation
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	76,527	60,978	146,076	153,897
Export \| Industrial
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	340,185	232,874	592,485	409,440
Export \| Metallurgical
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	$ 320,056	$ 300,155	$ 626,043	$ 649,113