Amount of interest expense classified as operating and nonoperating. Includes, but is not limited to, cost of borrowing accounted for as interest expense.

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Contract Obligations (Narrative) (Details) - Prepaid Coal Supply Liability - Stanwell [Member] T in Millions, $ in Millions, $ in Millions		3 Months Ended	6 Months Ended
	Jun. 10, 2025 USD ($) T	Jun. 30, 2025 USD ($)	Jun. 30, 2025 USD ($)	Jun. 10, 2025 AUD ($)	Jun. 10, 2025 USD ($)
Contract Obligations [Line Items]
Interest expense		$ 0.7	$ 0.7
Prepaid coal supply liability interest rate	13.00%
Amount of near-term liquidity provided from agreement	$ 150.0
Prepayment future coal sales				$ 116.1	$ 75.0
Prepayment, discount period	5 years
Estimated value of rebate	$ 75.0
Non-market portion of coal leases \| T	0.8