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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Description of Business, Basis of Presentation (Narrative) (Details) $ in Thousands, $ in Millions			3 Months Ended				6 Months Ended
	Jun. 18, 2025 USD ($)	Jun. 10, 2025 USD ($)	Jun. 30, 2025 USD ($)	Mar. 31, 2025 USD ($)	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Jun. 10, 2025 AUD ($)	Jun. 10, 2025 USD ($)	Dec. 31, 2024
Debt Instrument [Line Items]
Net (loss) income			$ (76,203)	$ (96,198)	$ 45,200	$ (29,001)	$ (172,401)	$ 16,199
Net cash used in operating activities							40,088	$ 11,095
Aggregate sources of liquidity			284,000				284,000
Cash and cash equivalents			261,600				$ 261,600
Prepaid Coal Supply Liability - Stanwell [Member]
Debt Instrument [Line Items]
Prepayment future coal sales									$ 116.1	$ 75,000
Estimated value of rebate		$ 75,000
Coal delivery period							5 years
Asset Based Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Remaining available amount			$ 22,400				$ 22,400
Credit facility, maximum borrowing capacity	$ 150,000
Stated interest rate			15.00%				15.00%
Credit facility, availability period							12 months
Asset-Based Lending Facility [Member]
Debt Instrument [Line Items]
Remaining available amount	75,000
Credit facility, maximum borrowing capacity	150,000
Draw from revolving facility	$ 75,000
Credit facility, availability period	12 months
9.25% Senior Secured Notes Due In 2029 [Member]
Debt Instrument [Line Items]
Stated interest rate			9.25%				9.25%				9.25%