Revenue From Contracts With Customers - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	$ 1,002,543	$ 553,432	$ 3,122,310	$ 1,590,841
Total Coal Revenue
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	993,781	542,145	3,096,402	1,556,225
Power Generation
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	483,303	238,106	1,393,643	701,277
Industrial
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	210,733	198,141	686,343	585,090
Metallurgical
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	299,745	105,898	1,016,416	269,858
Third-Party Terminal Revenue
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	5,591	7,490	15,087	22,689
Other Revenue
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	3,171	3,797	10,821	11,927
Domestic | Total Coal Revenue
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	478,430	174,454	1,368,601	560,017
Domestic | Power Generation
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	398,529	163,769	1,154,972	515,159
Domestic | Industrial
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	32,324	2,485	98,494	13,636
Domestic | Metallurgical
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	47,577	8,200	115,135	31,222
Export | Total Coal Revenue
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	515,351	367,691	1,727,801	996,208
Export | Power Generation
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	84,774	74,337	238,671	186,118
Export | Industrial
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	178,409	195,656	587,849	571,454
Export | Metallurgical
Disaggregation of Revenue [Line Items]
Total Revenue from Contracts with Customers	$ 252,168	$ 97,698	$ 901,281	$ 238,636