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Long-term Debt - Narrative (Details)		3 Months Ended				9 Months Ended		12 Months Ended
	Mar. 07, 2022 USD ($)	Sep. 30, 2022 USD ($) d $ / shares shares	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) d $ / shares shares	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($) shares	Mar. 01, 2025 USD ($)	Oct. 26, 2022	Oct. 17, 2022 USD ($)	Sep. 19, 2022 USD ($)	Jul. 25, 2022 USD ($)	Mar. 01, 2022 USD ($)	Feb. 24, 2022 $ / shares	Jan. 14, 2022 USD ($)	Jan. 29, 2021 USD ($)	Nov. 06, 2020 USD ($)
Debt Instrument [Line Items]
Debt issuance cost		$ 21,500,000				$ 21,500,000		$ 34,800,000
Interest expense		33,800,000			$ 45,500,000	110,800,000	$ 143,300,000
Net loss (gain) on early debt extinguishment		8,700,000			(16,000,000.0)	34,500,000	(31,300,000)
Finance lease obligations		25,700,000				25,700,000		29,300,000
Letters of credit outstanding, amount		$ 505,400,000				505,400,000
Proceeds from common stock issuances, net of costs						222,000,000.0	177,200,000
Debt Instrument, Exchange Offer, Required Purchase, Percentage Of Accreted Value		25.00%
Interest Paid, Capitalized, Investing Activities		$ 26,400,000			$ 40,000,000.0	$ 104,200,000	$ 144,300,000
Retirement of Debt								$ 270,900,000
Letter of Credit
Debt Instrument [Line Items]
Stated interest rate		0.75%				0.75%
Line of credit facility, maximum borrowing capacity		$ 250,000,000				$ 250,000,000
Common Stock
Debt Instrument [Line Items]
Common stock, shares issued (in shares) | shares		187,100,000				187,100,000		176,300,000
Common stock, shares authorized (in shares) | shares		450,000,000.0				450,000,000.0		450,000,000.0
Convertible Debt
Debt Instrument [Line Items]
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, Consideration Received on Transaction	$ 225,000,000
Debt for Equity Exchange
Debt Instrument [Line Items]
Proceeds from common stock issuances, net of costs								$ 106,100,000
Common stock, shares issued (in shares) | shares								10,000,000
Open Market Purchase
Debt Instrument [Line Items]
Payment for debt extinguishment or debt prepayment cost								$ 232,400,000
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 (2028 Convertible Notes)
Debt Instrument [Line Items]
Debt Instrument, Convertible, Threshold Consecutive Trading Days		30
Debt Instrument, Convertible, Threshold Trading Days		20
Senior Secured Term Loan due 2024 (Co-Issuer Term Loans)
Debt Instrument [Line Items]
Debt instrument, repurchase amount		$ 3,800,000				$ 3,800,000
Debt Securities, Available-for-Sale, Weighted Average Yield		105.91%				105.91%
Senior Secured Term Loan due 2024 (Co-Issuer Term Loans) | Increase
Debt Instrument [Line Items]
Debt Instrument, Exchange Offer, Required Purchase Amount		$ 43,900,000				$ 43,900,000
Senior Secured Term Loan due 2024 (Co-Issuer Term Loans) | Weighted Average
Debt Instrument [Line Items]
Debt instrument, repurchase amount		4,000,000				4,000,000
10.00% Revolving Credit Facility maturing 2025
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity				$ 225,000,000
Proceeds from Issuance or Sale of Equity						$ 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
Senior Secured Term Loan Due 2025 and 6.375% Senior Secured Notes due March 2025
Debt Instrument [Line Items]
Retirement of Debt		48,800,000
Payment for debt extinguishment or debt prepayment cost		46,600,000
8.500% Senior Secured Notes due December 20242 and 6.375% Senior Secured Notes due March 2025 [Domain]
Debt Instrument [Line Items]
Net loss (gain) on early debt extinguishment						$ 23,000,000
10.000% Senior Secured Notes due December 2024, Senior Secured Term Loan due 2024, 6.375% Senior Secured Notes due March 2025, and Senior Secured Term Loan due 2025
Debt Instrument [Line Items]
Net loss (gain) on early debt extinguishment		$ 8,700,000				$ 11,500,000
10.000% Senior Secured Notes due December 2024 and Senior Secured Term Loan due 2024
Debt Instrument [Line Items]
Debt Instrument, Covenant, Liquidity Attributable To Co-Issuers																	$ 60,000,000
Debt Instrument, Exchange Offer, Required Purchase, Percentage Of Accreted Value		103.91%
Mandatory principal prepayment, if required, period payable, threshold		$ 65,100,000		105,600,000
Debt Securities, Available-for-Sale, Weighted Average Yield		103.91%				103.91%
LC Agreement
Debt Instrument [Line Items]
Cash collateral posted				28,500,000
Debt repurchase, amount				30,000,000
LC Agreement | Subsequent Event
Debt Instrument [Line Items]
Debt Instrument, Exchange Offer, Required Purchase Amount											$ 12,200,000
Debt Instrument, Exchange Offer, Required Purchase, Percent of Accreted Value											95.57%
Senior Notes | 3.250% Convertible Senior Notes due March 2028 (2028 Convertible Notes)
Debt Instrument [Line Items]
Stated interest rate		3.25%				3.25%
Long-term debt		$ 320,000,000.0				$ 320,000,000.0		0
Principal amount														$ 320,000,000
Debt Issuance Costs, Gross		11,200,000				$ 11,200,000
Debt Instrument, Convertible, Threshold Consecutive Trading Days | d						30
Debt Instrument, Principle Amount		$ 1,000				$ 1,000
Common Stock, Excess of the Conversion Price, Percentage		130.00%				130.00%
Principle Amount, Percentage		98.00%				98.00%
Debt Instrument, Convertible, Conversion Price | $ / shares		$ 19.85				$ 19.85
Conversion Price Premium, Percent															32.50%
Debt instrument, convertible, conversion ratio		50.3816				50.3816
Senior Notes | 3.250% Convertible Senior Notes due March 2028 (2028 Convertible Notes) | Subsequent Event
Debt Instrument [Line Items]
Principle Amount, Percentage									100.00%
Aggregate Principle Amount, Notes Outstanding									$ 75,000,000
Senior Notes | 3.250% Convertible Senior Notes due March 2028 (2028 Convertible Notes) | Minimum
Debt Instrument [Line Items]
Debt Instrument, Convertible, Threshold Consecutive Trading Days		20
Senior Notes | 6.000% Senior Secured Notes due March 2022 (2022 Notes)
Debt Instrument [Line Items]
Stated interest rate		6.00%				6.00%
Long-term debt		$ 0				$ 0		23,100,000
Debt repurchase, amount						$ 23,100,000
Senior Notes | 6.375% Senior Secured Notes due March 2025 (2025 Notes)
Debt Instrument [Line Items]
Stated interest rate		6.375%				6.375%
Long-term debt		$ 66,200,000				$ 66,200,000		334,900,000
Debt repurchase, 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%				8.50%
Long-term debt		$ 0				$ 0		62,600,000
Debt Instrument, Exchange Offer, Required Purchase Amount																$ 38,600,000
Debt Instrument, Exchange Offer, Required Purchase, Percent of Accreted Value																94.94%
Debt repurchase, amount				100,000		$ 62,600,000
Senior Notes | 10.000% Senior Secured Notes due December 2024 (2024 Co-Issuer Notes)
Debt Instrument [Line Items]
Stated interest rate		10.00%				10.00%
Long-term debt		$ 81,600,000				$ 81,600,000		193,900,000
Debt Instrument, Exchange Offer, Required Purchase Amount												$ 81,600,000
Mandatory principal prepayment, if required, period payable, threshold		$ 27,200,000
Debt instrument, repurchase amount													$ 97,500,000
Debt Securities, Available-for-Sale, Weighted Average Yield												105.91%
30 day repurchase threshold | d		30				30
Debt repurchase, amount		$ 18,200,000		300,000
debt instrument, exchange offer, purchase amount required			$ 50,000,000
Senior Notes | 10.000% Senior Secured Notes due December 2024 (2024 Co-Issuer Notes) | Increase
Debt Instrument [Line Items]
Debt Instrument, Exchange Offer, Required Purchase Amount		$ 93,900,000				$ 93,900,000
Senior Notes | 10.00% Revolving Credit Facility maturing 2025
Debt Instrument [Line Items]
Stated interest rate		10.00%				10.00%
Line of credit facility, maximum borrowing capacity	$ 150,000,000
Term Loan | Senior Secured Term Loan due 2024 (Co-Issuer Term Loans)
Debt Instrument [Line Items]
Long-term debt		$ 114,600,000				$ 114,600,000		206,000,000.0
Debt Instrument, Exchange Offer, Required Purchase Amount			$ 50,000,000
Mandatory principal prepayment, if required, period payable, threshold		37,900,000
Debt instrument, repurchase amount		20,400,000				20,400,000
Debt Securities, Available-for-Sale, Weighted Average Yield			103.91%									105.91%
Solicited bid under debt auction		75,000,000
Debt repurchase, amount				$ 17,200,000
Term Loan | Senior Secured Term Loan due 2024 (Co-Issuer Term Loans) | Increase
Debt Instrument [Line Items]
Debt Instrument, Exchange Offer, Required Purchase Amount		61,200,000				61,200,000
Term Loan | Senior Secured Term Loan due 2024 (Co-Issuer Term Loans) | Weighted Average
Debt Instrument [Line Items]
Debt instrument, repurchase amount		21,600,000	$ 52,000,000			21,600,000
Term Loan | Senior Secured Term Loan due 2025, net of original issue discount (Senior Secured Term Loan)
Debt Instrument [Line Items]
Long-term debt		$ 282,600,000				$ 282,600,000		$ 322,800,000
Basis spread on variable rate						2.75%
Term Loan | Senior Secured Term Loan due 2025, net of original issue discount (Senior Secured Term Loan) | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate		5.83%				5.83%
Term Loan | Senior Secured Term Loan due 2025, net of original issue discount (Senior Secured Term Loan) | Subsequent Event | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate										6.33%
Line of credit | Letter of Credit
Debt Instrument [Line Items]
Debt Instrument, Covenant, Aggregate Liquidity At End Of Each Quarter		$ 125,000,000				$ 125,000,000
Surety Bond
Debt Instrument [Line Items]
Transaction support agreements, additional collateral to be posted																		$ 75,000,000

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