Long-term Debt Textuals (Details)	3 Months Ended									9 Months Ended		12 Months Ended		15 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Apr. 01, 2017 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Sep. 30, 2023 USD ($)	Nov. 30, 2020 USD ($)	Aug. 09, 2018 USD ($)	Apr. 11, 2018	Sep. 18, 2017 USD ($)	Apr. 03, 2017 USD ($)	Feb. 15, 2017 USD ($)
Debt Instrument [Line Items]
Interest expense, adequate protection payments									$ 29,800,000
Contractual interest expense									92,900,000
Debt issuance cost	$ 55,500,000				$ 68,900,000							$ 55,500,000	$ 68,900,000
Interest expense	36,800,000	$ 35,400,000	$ 36,000,000.0	$ 35,800,000	36,500,000	$ 38,200,000	$ 38,300,000	$ 36,300,000	32,900,000		$ 119,700,000	144,000,000.0	149,300,000
Repayment of Long-term Debt, Long-term Lease Obligation, and Capital Security									2,100,000		541,800,000	71,100,000	85,000,000.0
2019 Revolver availability	498,600,000											498,600,000
Loss on early debt extinguishment									0		(20,900,000)	(200,000)	(2,000,000.0)
Payments of Debt Issuance Costs									$ 45,400,000		$ 10,800,000	6,400,000	21,200,000
Capital lease and other obligations	$ 15,200,000				40,000,000.0							$ 15,200,000	40,000,000.0
Senior Notes | 6.000% Senior Secured Notes due March 2022
Debt Instrument [Line Items]
Stated interest rate	6.00%											6.00%
Debt Instrument, Restricted Payments, Amount Paid																	$ 10.00
Debt Instrument, Restricted Payments, Principal Amount Used to Calculate Payments																	1,000
Debt Instrument Repurchase Amount	$ 41,000,000.0											$ 41,000,000.0
Debt Instrument Repurchase Amount, excluding interest	$ 39,900,000											39,900,000
Write off of Deferred Debt Issuance Cost												1,300,000
Loss on early debt extinguishment												$ 200,000
Senior Notes | 6.375% Senior Secured Notes due March 2025
Debt Instrument [Line Items]
Stated interest rate	6.375%											6.375%
Debt Instrument, Restricted Payments, Amount Paid																	30.00
Debt Instrument, Restricted Payments, Principal Amount Used to Calculate Payments																	1,000
Senior Notes | 6.00% And 6.375% Senior Secured Notes, Successor Notes
Debt Instrument [Line Items]
Debt issuance cost																					$ 49,500,000
Interest expense												$ 72,000,000.0	71,900,000
Senior Notes | Successor Credit Agreement
Debt Instrument [Line Items]
Debt Instrument, Restricted Payments Basket	$ 150,000,000.0											150,000,000.0					650,000,000.0
Other Expenses													1,500,000
Debt Instrument, Restricted Payments Basket, Annual Limit																	150,000,000.0
2013 Revolver | 2017 Revolver
Debt Instrument [Line Items]
Debt issuance cost	4,700,000	5,700,000								$ 5,700,000		4,700,000
Interest expense													7,200,000
Unrestricted Cash, Net Limit	800,000,000.0											800,000,000.0
Line of Credit Facility, Maximum Borrowing Capacity	$ 350,000,000.0	565,000,000.0								$ 565,000,000.0		$ 350,000,000.0
Financing Facility, Base Interest Rate	3.375%											3.375%
Revolving Credit Facility, Fee on Unused Borrowings	0.50%											0.50%
Aggregate Letters of Credit, Maximum	$ 66,400,000											$ 66,400,000
2013 Revolver | 2019 Revolver
Debt Instrument [Line Items]
Interest expense												6,200,000
Senior Secured Term Loan due 2025, net of original issue discount | Successor Credit Agreement
Debt Instrument [Line Items]
Principal amount	$ 400,000,000.0											400,000,000.0
Interest expense												$ 22,200,000	24,000,000.0
Debt Instrument, Restricted Payments Basket																	$ 19,800,000		$ 450,000,000.0
Other Expenses													$ 900,000
Basis spread on variable rate												2.75%
Floor interest rate																		1.00%
Debt Instrument, Voluntary Principal Prepayment	101.00%											101.00%
Mandatory principal prepayment, percent of excess cash flow	75.00%											75.00%
Mandatory principal prepayment, if required, period payable, threshold												100 days
Excess proceeds from sales of assets, threshold ($10 million or greater)	$ 10,000,000.0											$ 10,000,000.0
Payment for debt extinguishment or debt prepayment cost														$ 546,000,000.0
Debt Instrument, Covenant, Fixed Charge Coverage Ratio											2.00		2.25
Repayments of Debt							$ 46,000,000.0					557,000,000.0
Loss on early debt extinguishment											$ 20,900,000		$ (2,000,000.0)
Debt Instrument, Fee Amount					$ 2,000,000.0								2,000,000.0
Payments of Debt Issuance Costs													$ 1,000,000.0
Restricted payments threshold	450,000,000.0											450,000,000.0							$ 50,000,000.0
Senior Secured Term Loan due 2025, net of original issue discount | Senior Secured Term Loan due 2025, net of original issue discount
Debt Instrument [Line Items]
Original issue discount and deferred finance costs	$ 37,300,000										$ 6,100,000	$ 37,300,000
Secured Debt																				$ 950,000,000.0
Debt Instrument, Redemption, Period One | Senior Notes | 6.000% Senior Secured Notes due March 2022
Debt Instrument [Line Items]
Redemption price, percentage												103.00%
Debt Instrument, Redemption, Period One | Senior Notes | 6.375% Senior Secured Notes due March 2025
Debt Instrument [Line Items]
Redemption price, percentage												104.80%
Debt Instrument, Redemption, Period Two | Senior Notes | 6.000% Senior Secured Notes due March 2022
Debt Instrument [Line Items]
Redemption price, percentage												101.50%
Debt Instrument, Redemption, Period Two | Senior Notes | 6.375% Senior Secured Notes due March 2025
Debt Instrument [Line Items]
Redemption price, percentage												103.20%
Debt Instrument, Redemption, Period Three | Senior Notes | 6.375% Senior Secured Notes due March 2025
Debt Instrument [Line Items]
Redemption price, percentage												101.60%
Peabody Investments (Gibraltar) Limited | Senior Notes | 6.00% And 6.375% Senior Secured Notes, Successor Notes
Debt Instrument [Line Items]
Collateral, non-voting capital stock, percent	100.00%											100.00%
Collateral, voting capital stock, percent	65.00%											65.00%
London Interbank Offered Rate (LIBOR) | 2013 Revolver | 2017 Revolver
Debt Instrument [Line Items]
Basis spread on variable rate										3.25%
London Interbank Offered Rate (LIBOR) | Senior Secured Term Loan due 2025, net of original issue discount | Successor Credit Agreement
Debt Instrument [Line Items]
Basis spread on variable rate													2.75%
Total Leverage Ratio Less or Equal to 2.00 to 1.00 Greater Than 1.50 to 1.00 | Senior Secured Term Loan due 2025, net of original issue discount | Successor Credit Agreement
Debt Instrument [Line Items]
Mandatory principal prepayment, percent of excess cash flow	50.00%											50.00%
Total Leverage Ratio Less or Equal to 2.00 to 1.00 Greater Than 1.50 to 1.00 | Maximum | Senior Secured Term Loan due 2025, net of original issue discount | Successor Credit Agreement
Debt Instrument [Line Items]
Total Leverage Ratio	2.00											2.00
Total Leverage Ratio Less or Equal to 2.00 to 1.00 Greater Than 1.50 to 1.00 | Minimum | Senior Secured Term Loan due 2025, net of original issue discount | Successor Credit Agreement
Debt Instrument [Line Items]
Total Leverage Ratio	1.50											1.50
Total Leverage Ratio Less or Equal to 1.50 to 1.00 Greater Than 1.00 to 1.00 | Senior Secured Term Loan due 2025, net of original issue discount | Successor Credit Agreement
Debt Instrument [Line Items]
Mandatory principal prepayment, percent of excess cash flow	25.00%											25.00%
Total Leverage Ratio Less or Equal to 1.50 to 1.00 Greater Than 1.00 to 1.00 | Maximum | Senior Secured Term Loan due 2025, net of original issue discount | Successor Credit Agreement
Debt Instrument [Line Items]
Total Leverage Ratio	1.50											1.50
Total Leverage Ratio Less or Equal to 1.50 to 1.00 Greater Than 1.00 to 1.00 | Minimum | Senior Secured Term Loan due 2025, net of original issue discount | Successor Credit Agreement
Debt Instrument [Line Items]
Total Leverage Ratio	1.00											1.00
Total Leverage Ratio Less or Equal to 1.00 to 1.00 | Senior Secured Term Loan due 2025, net of original issue discount | Successor Credit Agreement
Debt Instrument [Line Items]
Mandatory principal prepayment, percent of excess cash flow	0.00%											0.00%
Total Leverage Ratio	1.00											1.00
Total Leverage Ration Less Or Equal 2.00 to 1.00 [Member] | 2013 Revolver | 2017 Revolver
Debt Instrument [Line Items]
Total Leverage Ratio	2.00											2.00
Total Leverage Ration Less Or Equal 2.00 to 1.00 [Member] | Senior Secured Term Loan due 2025, net of original issue discount | Successor Credit Agreement
Debt Instrument [Line Items]
Total Leverage Ratio	2.00											2.00
Total Leverage Ratio Less or Equal 1.25 to 1.00 | Senior Secured Term Loan due 2025, net of original issue discount | Successor Credit Agreement
Debt Instrument [Line Items]
Total Leverage Ratio	1.25											1.25
Dividend payment and stock purchase payment threshold	$ 25,000,000.0	$ 25,000,000.0								$ 25,000,000.0		$ 25,000,000.0
2013 Revolver | Line of Credit | 2017 Revolver
Debt Instrument [Line Items]
Long-term debt	$ 350,000,000.0											$ 350,000,000.0
Geographic Distribution, Domestic [Member] | Senior Notes | 6.00% And 6.375% Senior Secured Notes, Successor Notes
Debt Instrument [Line Items]
Collateral, capital stock, percent	100.00%											100.00%
Export | Senior Notes | 6.00% And 6.375% Senior Secured Notes, Successor Notes
Debt Instrument [Line Items]
Collateral, non-voting capital stock, percent	100.00%											100.00%
Collateral, voting capital stock, percent	65.00%											65.00%
Effect of Plan | Senior Notes | 6.000% Senior Secured Notes due March 2022
Debt Instrument [Line Items]
Principal amount																					500,000,000.0
Effect of Plan | Senior Notes | 6.375% Senior Secured Notes due March 2025
Debt Instrument [Line Items]
Principal amount																					$ 500,000,000.0
Effect of Plan | Senior Secured Term Loan due 2025, net of original issue discount | Successor Credit Agreement
Debt Instrument [Line Items]
Principal amount																				$ 950,000,000.0
Forecast | 2013 Revolver | 2017 Revolver
Debt Instrument [Line Items]
2019 Revolver commitments, matures 2023															$ 540,000,000.0
2019 Revolver commitments, matures 2020																$ 25,000,000.0