Equity Method Investments - Textual (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2021 AUD ($)
Schedule of Equity Method Investments [Line Items]
Cash receipts from Middlemount	$ (500,000)	$ (23,200,000)	$ (27,300,000)
Net income (loss)	371,400,000	(1,873,800,000)	(185,100,000)
Changes in tax reserves	1,900,000	(7,700,000)	3,000,000.0
Revenues	3,318,300,000	2,881,100,000	4,623,400,000
Equity method investment, current assets	1,801,700,000	1,420,300,000
Equity method investment, current liabilities	931,700,000	790,600,000
Insurance recovery	0	0	125,000,000.0
Equity method investment and financing receivables related to Middlemount
Schedule of Equity Method Investments [Line Items]
Insurance recovery	$ 12,500,000
Performance Units
Schedule of Equity Method Investments [Line Items]
Stock price measurement period	3 years
Return on invested capital period	3 years
Equity method investment and financing receivables related to Middlemount
Schedule of Equity Method Investments [Line Items]
Cash receipts from Middlemount	$ 43,500,000	0	14,700,000
Equity interest percentage of revolving loans limit	50.00%			50.00%
Revolving loan limit				$ 50
Financing receivable, stated interest rate (in percent)	10.00%
Intercompany loans, carrying value		46,200,000
Equity method investment and financing receivables related to Middlemount
Schedule of Equity Method Investments [Line Items]
Net income (loss)			17,000,000
Valuation allowance	$ 33,000,000	33,000,000
Revenues	265,000,000	123,000,000	$ 160,000,000
Equity method investment, current assets	83,100,000	31,000,000
Equity method investment ,noncurrent assets	$ 269,900,000	301,800,000
Ownership percentage of equity method investment	50.00%			50.00%
Equity method investment, current liabilities	$ 254,900,000	273,800,000
Equity method investment, noncurrent liabilities	$ 79,500,000	$ 83,500,000