Long-Term Debt - Narrative (Details) - USD ($)			1 Months Ended	12 Months Ended
	Mar. 27, 2025	Jan. 13, 2025	Jan. 31, 2025	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Segment assets				$ 6,130,053,000	$ 2,879,543,000	$ 2,675,003,000
Net (Loss) Income				(153,216,000)	286,405,000	655,892,000
Loss on extinguishment of debt				11,680,000	0	2,725,000
Arch Resources, Inc
Debt Instrument [Line Items]
Purchase price consideration		$ 98,075,000
Accounts Receivable Securitization Facility | Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 250,000,000
Reduced annual rate				0.10%
Letters of credit outstanding				$ 158,282,000	71,922,000
Available borrowing capacity				26,840,000	42,000
Borrowings under the facility				0	0	0
Payments under the facility				$ 0	$ 0	0
PEDFA Bonds
Debt Instrument [Line Items]
Letters of credit outstanding	$ 75,000,000
Debt instrument, face amount	$ 97,560,000
Stated interest rate percentage	5.45%			5.45%	9.00%
Debt instrument, term	10 years
MEDCO Bonds
Debt Instrument [Line Items]
Letters of credit outstanding	$ 102,865,000
Debt instrument, face amount	$ 102,865,000
Stated interest rate percentage	5.00%			5.00%	5.75%
Debt instrument, term	10 years
WVEDA Bonds
Debt Instrument [Line Items]
Debt instrument, face amount	$ 106,355,000
Stated interest rate percentage	5.45%			5.45%	5.45%
Debt instrument, term	10 years
Non-Guarantor Subsidiaries
Debt Instrument [Line Items]
Segment assets				$ 350,156,000	$ 133,853,000
Accounts receivable, after allowance for credit loss				347,093,000	133,694,000
Net (Loss) Income				10,575,000	46,000	$ 5,129,000
Revolving Credit Facility
Debt Instrument [Line Items]
Long-term line of credit				$ 0	0
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 600,000,000		355,000,000
Period for outstanding amounts prior to stated maturity			91 days
Liquidity requirement			$ 250,000,000
Reduced annual rate			0.75%	0.10%
Letters of credit outstanding				$ 110,098,000	107,087,000
Available borrowing capacity				$ 489,902,000	$ 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
Debt instrument, covenant, fixed charge coverage ratio, minimum				3.00
Debt instrument, covenant, first lien gross leverage ratio, actual				0.28
Debt instrument, covenant, net leverage ratio, actual				0.03
Debt instrument, covenant, fixed charge coverage ratio, actual				35.10
Revolving Credit Facility and TLA Facility | Line of Credit | Maximum
Debt Instrument [Line Items]
Debt instrument, covenant, first lien gross leverage ratio				1.50
Series 2020 | WVEDA Bonds
Debt Instrument [Line Items]
Letters of credit outstanding	$ 53,090,000
Series 2021 | WVEDA Bonds
Debt Instrument [Line Items]
Letters of credit outstanding	$ 44,985,000