Segment Information - Schedule of Segment Reporting Information by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Segment Reporting Information [Line Items]
Total Revenue from Contracts with Customers	$ 1,102,361	$ 490,720	$ 2,119,767	$ 1,037,409
Adjusted EBITDA	144,270	124,538	267,755	306,291
Segment Assets	6,208,738	2,710,454	6,208,738	2,710,454	$ 2,879,543
Capital Expenditures	89,185	55,408	154,007	97,760
Other, Corporate and Eliminations
Segment Reporting Information [Line Items]
Total Revenue from Contracts with Customers	(13,577)	(3,555)	(26,652)	(13,219)
Cash Costs of Revenue	3,211	3,263	6,038	5,457
Transportation Costs	(18,032)	(7,293)	(34,302)	(21,349)
Other Segment Items	61,790	26,112	103,978	37,031
Adjusted EBITDA	(60,546)	(25,637)	(102,366)	(34,358)
Segment Assets	1,353,473	840,704	1,353,473	840,704
Capital Expenditures	6,550	2,742	9,675	3,980
High CV Thermal | Operating Segments
Segment Reporting Information [Line Items]
Total Revenue from Contracts with Customers	606,500	454,752	1,148,586	951,481
Cash Costs of Revenue	331,058	230,262	634,619	472,698
Transportation Costs	99,084	70,310	192,813	150,852
Other Segment Items	0	928	0	(1,322)
Adjusted EBITDA	176,358	153,252	321,154	329,253
Segment Assets	2,072,304	1,665,463	2,072,304	1,665,463
Capital Expenditures	48,175	47,043	82,170	84,001
Metallurgical | Operating Segments
Segment Reporting Information [Line Items]
Total Revenue from Contracts with Customers	299,994	27,503	604,574	62,599
Cash Costs of Revenue	214,365	33,842	425,140	68,468
Transportation Costs	67,088	2,623	144,070	5,979
Other Segment Items	21,243	0	57,649	0
Adjusted EBITDA	(2,702)	(8,962)	(22,285)	(11,848)
Segment Assets	2,334,353	118,842	2,334,353	118,842
Capital Expenditures	30,509	1,886	54,473	4,979
PRB | Operating Segments
Segment Reporting Information [Line Items]
Total Revenue from Contracts with Customers	186,872	0	349,461	0
Cash Costs of Revenue	168,246	0	301,404	0
Transportation Costs	2,460	0	5,200	0
Other Segment Items	0	0	0	0
Adjusted EBITDA	16,166	0	42,857	0
Segment Assets	361,452	0	361,452	0
Capital Expenditures	2,413	0	4,909	0
Baltimore Marine Terminal | Operating Segments
Segment Reporting Information [Line Items]
Total Revenue from Contracts with Customers	22,572	12,020	43,798	36,548
Cash Costs of Revenue	7,578	6,135	15,403	13,304
Transportation Costs	0	0	0	0
Other Segment Items	0	0	0	0
Adjusted EBITDA	14,994	5,885	28,395	23,244
Segment Assets	87,156	85,445	87,156	85,445
Capital Expenditures	$ 1,538	$ 3,737	$ 2,780	$ 4,800