Long-term Debt - Narrative (Details) $ / shares in Units, $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	May 31, 2023 $ / shares	Dec. 31, 2022 USD ($)	Mar. 01, 2022 USD ($)
Debt Instrument [Line Items]
Debt issuance cost	$ 9.0			$ 9.0			$ 9.8
Interest expense	13.3	$ 37.6		31.7	$ 77.0
Net loss on early debt extinguishment	2.0	2.3		8.8	25.8
Finance lease obligations	23.5			23.5			23.6
Interest Paid, Capitalized, Investing Activities	$ 22.9	$ 40.6		41.9	$ 77.8
Dividends Payable, Amount Per Share | $ / shares						$ 0.075
3.250% Convertible Senior Notes due March 2028 (2028 Convertible Notes)
Debt Instrument [Line Items]
Debt Instrument, Convertible, If-converted Value in Excess of Principal				$ 29.2
8.500% Senior Secured Notes due December 20242 and 6.375% Senior Secured Notes due March 2025 [Domain]
Debt Instrument [Line Items]
Net loss on early debt extinguishment			$ 23.0
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	$ 320.0			$ 320.0			$ 320.0
Principal amount								$ 320.0
Debt Issuance Costs, Gross			11.2
Debt Conversion, Converted Instrument, Rate	1.00%
Debt Instrument, Convertible, Conversion Ratio	50.3816
Debt Instrument, Convertible, Conversion Ratio, Revised	50.5451
Senior Notes | 6.375% Senior Secured Notes due March 2025 (2025 Notes)
Debt Instrument [Line Items]
Debt repurchase, amount			257.4
Senior Notes | 8.500% Senior Secured Notes due December 2024 (2024 Peabody Notes)
Debt Instrument [Line Items]
Debt repurchase, amount			$ 62.6