Long-Term Debt - Narrative (Details) - USD ($)			1 Months Ended	3 Months Ended						9 Months Ended
	Mar. 27, 2025	Jan. 13, 2025	Jan. 31, 2025	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024	Jan. 30, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Segment Assets				$ 6,195,888,000			$ 2,824,117,000			$ 6,195,888,000	$ 2,824,117,000		$ 2,879,543,000
Net income				31,598,000	$ (36,556,000)	$ (69,277,000)	95,632,000	$ 58,061,000	$ 101,891,000	(74,235,000)	255,584,000
Loss on extinguishment of debt				$ 0			0			$ 11,680,000	0
Arch Resources, Inc
Debt Instrument [Line Items]
Purchase price consideration		$ 98,075,000
WVEDA Solid Waste Disposal Facility Revenue Bonds due March 2035 at 5.45%
Debt Instrument [Line Items]
Debt instrument, face amount	$ 106,355,000
Debt instrument, interest rate, stated percentage	5.45%			5.45%						5.45%			5.45%
Debt instrument, term	10 years
MEDCO Port Facilities Refunding Revenue Bonds due March 2035 at 5.00% and 5.75% at September 30, 2025 and December 31, 2024, respectively
Debt Instrument [Line Items]
Letters of credit outstanding, amount	$ 102,865,000
Debt instrument, face amount	$ 102,865,000
Debt instrument, interest rate, stated percentage	5.00%			5.00%						5.00%			5.75%
Debt instrument, term	10 years
PEDFA Solid Waste Disposal Facility Revenue Bonds due March 2035 at 5.45% and 9.00% at September 30, 2025 and December 31, 2024, respectively
Debt Instrument [Line Items]
Letters of credit outstanding, amount	$ 75,000,000
Debt instrument, face amount	$ 97,560,000
Debt instrument, interest rate, stated percentage	5.45%			5.45%						5.45%			9.00%
Debt instrument, term	10 years
Non-Guarantor Subsidiaries
Debt Instrument [Line Items]
Segment Assets				$ 326,734,000						$ 326,734,000			$ 133,853,000
Accounts receivable, after allowance for credit loss				325,591,000						325,591,000			133,694,000
Net income				3,776,000			$ 528,000			8,408,000	$ 775,000
Revolving Credit Facility
Debt Instrument [Line Items]
Long-term line of credit				0						$ 0			0
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			$ 600,000,000									$ 355,000,000
Reduced annual rate			0.75%							0.10%
Letters of credit outstanding, amount				78,663,000						$ 78,663,000			107,087,000
Line of credit facility, remaining borrowing capacity				$ 521,337,000						$ 521,337,000			$ 247,913,000
Revolving Credit Facility and TLA Facility | Line of Credit
Debt Instrument [Line Items]
Debt instrument, covenant, net leverage ratio, maximum				2.50						2.50
Debt instrument, covenant, fixed charge coverage ratio, minimum				3.00						3.00
Debt instrument, covenant, first lien gross leverage ratio, actual				0.18						0.18
Debt instrument, covenant, net leverage ratio, actual				(0.04)						(0.04)
Debt instrument, covenant, fixed charge coverage ratio, actual				50.13						50.13
Revolving Credit Facility and TLA Facility | Line of Credit | Maximum
Debt Instrument [Line Items]
Debt instrument, covenant, first lien gross leverage ratio				1.50						1.50
Series 2020 | WVEDA Solid Waste Disposal Facility Revenue Bonds due March 2035 at 5.45%
Debt Instrument [Line Items]
Letters of credit outstanding, amount	$ 53,090,000
Series 2021 | WVEDA Solid Waste Disposal Facility Revenue Bonds due March 2035 at 5.45%
Debt Instrument [Line Items]
Letters of credit outstanding, amount	$ 44,985,000