Accounts Receivable Securitization (Details) - Line of Credit - Accounts Receivable Securitization Facility - USD ($)	6 Months Ended
	Jun. 30, 2025	Jan. 14, 2025	Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Line of credit facility, maximum borrowing capacity	$ 100,000,000
Line of credit facility, unused capacity, commitment fee percentage	0.60%
Accounts receivable eligible for securitization	$ 48,639,000		$ 71,964,000
Line of credit facility, fair value of amount outstanding	0		0
Letters of credit outstanding, amount	48,437,000		71,922,000
Line of credit facility, remaining borrowing capacity	202,000		$ 42,000
Arch Resources, Inc
Accounts, Notes, Loans and Financing Receivable [Line Items]
Line of credit facility, maximum borrowing capacity		$ 150,000,000
Accounts receivable eligible for securitization	139,700,000
Letters of credit outstanding, amount	51,919,000
Line of credit facility, remaining borrowing capacity	$ 87,781,000
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Line of credit facility, commitment fee percentage	2.00%
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Line of credit facility, commitment fee percentage	2.50%