Long-term Debt - Narrative (Details)		3 Months Ended		12 Months Ended
	Mar. 07, 2022 USD ($)	Mar. 31, 2022 USD ($) d $ / shares shares	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) shares	Mar. 01, 2025	Mar. 01, 2022 USD ($)	Feb. 24, 2022 $ / shares	Jan. 29, 2021 USD ($)	Nov. 06, 2020 USD ($)
Debt Instrument [Line Items]
Debt issuance cost		$ 31,200,000		$ 34,800,000
Interest expense		39,400,000	$ 52,400,000
Net loss (gain) on early debt extinguishment		23,500,000	(3,500,000)
Total finance lease liabilities		27,600,000		$ 29,300,000
Letters of credit outstanding, amount		469,100,000
Proceeds from common stock issuances, net of costs		222,000,000.0	0
Proceeds from (Payments for) Deposits Applied to Debt Retirements		270,900,000
Payments for Deposits Applied to Debt Retirements		232,400,000
Interest Paid, Capitalized, Investing Activities		37,200,000	56,300,000
Extinguishment of Debt, Gain (Loss), Net of Tax		$ 23,000,000
Letter of Credit
Debt Instrument [Line Items]
Stated interest rate		0.75%
Line of credit facility, maximum borrowing capacity		$ 250,000,000
Common Stock
Debt Instrument [Line Items]
Common stock, shares issued (in shares) | shares		187,000,000.0		176,300,000
Common stock, shares authorized (in shares) | shares		450,000,000.0		450,000,000.0
Sale of Stock, Number of Shares Issued in Transaction | shares		10,000,000
Shares Issued, Price Per Share | $ / shares							$ 14.98
At Market Issuance
Debt Instrument [Line Items]
Sale of Stock, Number of Shares Issued in Transaction | shares				24,800,000
At Market Issuance | Common Stock
Debt Instrument [Line Items]
Sale of Stock, Description of Transaction	225.0 million
Common Stock
Debt Instrument [Line Items]
Proceeds from common stock issuances, net of costs		$ 106,100,000
Common Stock | At Market Issuance
Debt Instrument [Line Items]
Proceeds from common stock issuances, net of costs				$ 269,800,000
3.250% Convertible Senior Notes due March 2028
Debt Instrument [Line Items]
Interest expense		$ 1,000,000
10.00% Revolving Credit Facility maturing 2025
Debt Instrument [Line Items]
Line of Credit Facility, Borrowing Capacity, Description		225.0 million
Proceeds from lines of credit		$ 222,000,000
10.00% Revolving Credit Facility maturing 2025 | At Market Issuance | Common Stock
Debt Instrument [Line Items]
Sale of Stock, Number of Shares Issued in Transaction | shares		10,100,000
Surety Bond | Letter of Credit
Debt Instrument [Line Items]
Interest expense		$ 13,500,000	$ 10,900,000
Senior Notes | 6.000% Senior Secured Notes due March 2022 (2022 Notes)
Debt Instrument [Line Items]
Stated interest rate		6.00%
Long-term debt		$ 0		23,100,000
Payments for Deposits Applied to Debt Retirements		$ 23,100,000
Senior Notes | 6.375% Senior Secured Notes due March 2025 (2025 Notes)
Debt Instrument [Line Items]
Stated interest rate		6.375%
Long-term debt		$ 77,500,000		334,900,000
Debt Instrument, Debt Default, Amount		$ 257,400,000
Senior Notes | 8.500% Senior Secured Notes due December 2024 (2024 Peabody Notes)
Debt Instrument [Line Items]
Stated interest rate		8.50%
Long-term debt		$ 0		62,600,000
Debt Instrument, Exchange Offer, Required Purchase Amount				$ 38,600,000
Debt Instrument, Exchange Offer, Required Purchase, Percentage Of Accreted Value		0.25		0.94940
Debt Instrument Exchanged, Aggregate Principal Amount		$ 30,000,000		$ 100,000
Cash collateral or restricted cash requirement		$ 28,500,000
Senior Notes | 10.000% Senior Secured Notes due December 2024 (2024 Co-Issuer Notes)
Debt Instrument [Line Items]
Stated interest rate		10.00%
Net loss (gain) on early debt extinguishment		$ (500,000)
Long-term debt		193,600,000		193,900,000
Debt Instrument, Covenant, Liquidity Attributable To Co-Issuers								$ 60,000,000
Mandatory principal prepayment, if required, period payable, threshold		$ 105,600,000
Senior Notes | 3.250% Convertible Senior Notes due March 2028
Debt Instrument [Line Items]
Stated interest rate		3.25%
Long-term debt		$ 320,000,000.0		0
Principal amount						$ 320,000,000
Debt Issuance Costs, Gross		$ 11,200,000
Debt Instrument, Convertible, Threshold Consecutive Trading Days | d		30
Debt Instrument, Principle Amount		$ 1,000
Common Stock, Excess of the Conversion Price, Percentage		1.30
Principle Amount, Percentage		0.98
Conversion of Stock, Shares Issued | shares		50.3816
Debt Instrument, Convertible, Conversion Price | $ / shares		$ 19.85
Conversion Price Premium, Percent							0.325
Aggregate Principle Amount, Notes Outstanding		$ 75,000,000
Senior Notes | 3.250% Convertible Senior Notes due March 2028 | Subsequent Event
Debt Instrument [Line Items]
Principle Amount, Percentage					1
Senior Notes | 10.00% Revolving Credit Facility maturing 2025
Debt Instrument [Line Items]
Stated interest rate		10.00%
Line of credit facility, maximum borrowing capacity	$ 150,000,000
Senior Notes | Peabody Notes
Debt Instrument [Line Items]
Debt Instrument, Debt Default, Amount		$ 62,600,000
Senior Notes | New Co-Issuer Term Note
Debt Instrument [Line Items]
Mandatory principal prepayment, if required, period payable, threshold		300,000
Term Loan | Senior Secured Term Loan due 2024 (Co-Issuer Term Loans)
Debt Instrument [Line Items]
Long-term debt		188,800,000		206,000,000.0
Term Loan | Senior Secured Term Loan due 2025, net of original issue discount (Senior Secured Term Loan)
Debt Instrument [Line Items]
Long-term debt		$ 321,800,000		$ 322,800,000
Term Loan | Successor Credit Agreement | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis spread on variable rate		2.75%
Line of credit | Letter of Credit
Debt Instrument [Line Items]
Debt Instrument, Covenant, Aggregate Liquidity At End Of Each Quarter		$ 125,000,000
Surety Bond
Debt Instrument [Line Items]
Transaction support agreements, additional collateral to be posted									$ 75,000,000
Loans | New Co-Issuer Term Loans
Debt Instrument [Line Items]
Mandatory principal prepayment, if required, period payable, threshold		$ 17,200,000