Revenue Recognition - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Contract with customer, liability	$ 5,300,000,000
Accounts receivable, credit loss expense (reversal)	0		$ (4,400,000)
Revenues	3,318,300,000	$ 2,881,100,000	4,623,400,000
Corporate and Other
Disaggregation of Revenue [Line Items]
Revenues	$ (3,700,000)	(15,600,000)	80,500,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Disaggregation of Revenue [Line Items]
Revenue, remaining performance obligation, percentage	46.00%
Revenue, remaining performance obligation, period	12 months
Other (2)
Disaggregation of Revenue [Line Items]
Revenues	$ 15,400,000	17,400,000	128,700,000
Other (2) | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenues	(3,700,000)	(15,600,000)	80,500,000
Trading and Brokerage Coal Deliveries
Disaggregation of Revenue [Line Items]
Revenues		(28,500,000)	(18,800,000)
Trading and Brokerage Coal Deliveries | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenues	139,500,000	(28,900,000)	$ (17,600,000)
Trade Accounts Receivable
Disaggregation of Revenue [Line Items]
Accounts receivable, allowance for credit losses	0	0
Miscellaneous Receivables
Disaggregation of Revenue [Line Items]
Accounts receivable, allowance for credit losses	$ 800,000,000	$ 800,000,000