Equity Method Investments (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 AUD ($)	Dec. 31, 2021 USD ($)
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 12,300,000		$ 12,300,000			$ 62,200,000
Income (Loss) from Equity Method Investments	$ 48,700,000	$ (3,500,000)	93,400,000	$ (4,400,000)
Cash receipts from Middlemount Coal Pty Ltd and other related parties			143,900,000	2,600,000
Middlemount Mine
Schedule of Equity Method Investments [Line Items]
Cash receipts from Middlemount Coal Pty Ltd and other related parties			$ (143,200,000)	(2,300,000)
Equity interest percentage of revolving loans limit	50.00%		50.00%		50.00%
Revolving loan limit					$ 50,000,000
Financing receivable, stated interest rate (in percent)			10.00%
Middlemount Mine
Schedule of Equity Method Investments [Line Items]
Income (Loss) from Equity Method Investments	$ 49,500,000	$ (3,500,000)	$ 95,200,000	$ (4,400,000)