Long-term Debt - Textuals (Details) - USD ($) | 3 Months Ended | 9 Months Ended | 12 Months Ended | 30 Months Ended | | | | | | | |
Sep. 30, 2019 | Sep. 30, 2018 | Jun. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018 | Dec. 31, 2018 | Sep. 30, 2019 | Sep. 30, 2023 | Nov. 30, 2020 | Oct. 01, 2018 | Aug. 09, 2018 | Sep. 18, 2017 | Apr. 03, 2017 | Feb. 15, 2017 |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Debt issuance cost | $ 59,800,000 | | | $ 59,800,000 | | $ 68,900,000 | $ 59,800,000 | | | | | | | |
Interest expense | $ 35,400,000 | $ 38,200,000 | | 107,200,000 | $ 112,800,000 | | | | | | | | | |
Repayment of Long-term Debt, Long-term Lease Obligation, and Capital Security | | | | $ 23,900,000 | 73,000,000 | | | | | | | | | |
Successor Credit Agreement | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Debt Instrument, Covenant, Fixed Charge Coverage Ratio | 2.25 | | | | | | | | | | | | | |
Senior Notes | 6.000% Senior Secured Notes due March 2022 | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Stated interest rate | 6.00% | | | 6.00% | | 6.00% | 6.00% | | | | | | | |
Debt Instrument, Restricted Payments, Amount Paid | | | | | | | | | | | $ 10 | | | |
Debt Instrument, Restricted Payments, Principal Amount Used to Calculate Payments | | | | | | | | | | | 1,000 | | | |
Long-term debt | $ 500,000,000 | | | $ 500,000,000 | | $ 500,000,000 | $ 500,000,000 | | | | | | | |
Senior Notes | 6.000% Senior Secured Notes due March 2022 | Debt Instrument, Redemption, Period One | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Redemption price, percentage | 103.00% | | | | | | | | | | | | | |
Senior Notes | 6.000% Senior Secured Notes due March 2022 | Debt Instrument, Redemption, Period Two [Member] | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Redemption price, percentage | 101.50% | | | | | | | | | | | | | |
Senior Notes | 6.000% Senior Secured Notes due March 2022 | Effect of Plan | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Principal amount | | | | | | | | | | | | | | $ 500,000,000 |
Stated interest rate | | | | | | | | | | | | | | 6.00% |
Senior Notes | 6.375% Senior Secured Notes due March 2025 | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Stated interest rate | 6.375% | | | 6.375% | | 6.375% | 6.375% | | | | | | | |
Debt Instrument, Restricted Payments, Amount Paid | | | | | | | | | | | 30 | | | |
Debt Instrument, Restricted Payments, Principal Amount Used to Calculate Payments | | | | | | | | | | | 1,000 | | | |
Long-term debt | $ 500,000,000 | | | $ 500,000,000 | | $ 500,000,000 | $ 500,000,000 | | | | | | | |
Senior Notes | 6.375% Senior Secured Notes due March 2025 | Debt Instrument, Redemption, Period One | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Redemption price, percentage | 104.80% | | | | | | | | | | | | | |
Senior Notes | 6.375% Senior Secured Notes due March 2025 | Debt Instrument, Redemption, Period Two [Member] | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Redemption price, percentage | 103.20% | | | | | | | | | | | | | |
Senior Notes | 6.375% Senior Secured Notes due March 2025 | Debt Instrument, Redemption, Period Three [Member] | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Redemption price, percentage | 101.60% | | | | | | | | | | | | | |
Senior Notes | 6.375% Senior Secured Notes due March 2025 | Effect of Plan | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Principal amount | | | | | | | | | | | | | | $ 500,000,000 |
Stated interest rate | | | | | | | | | | | | | | 6.375% |
Senior Notes | 6.00% And 6.375% Senior Secured Notes, Successor Notes | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Debt issuance cost | $ 49,500,000 | | | 49,500,000 | | | $ 49,500,000 | | | | | | | |
Interest expense | $ 18,100,000 | 19,100,000 | | $ 54,200,000 | 54,000,000 | | | | | | | | | |
Senior Notes | 6.00% And 6.375% Senior Secured Notes, Successor Notes | Domestic | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Collateral, capital stock, percent | 100.00% | | | 100.00% | | | 100.00% | | | | | | | |
Senior Notes | 6.00% And 6.375% Senior Secured Notes, Successor Notes | Export | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Collateral, non-voting capital stock, percent | 100.00% | | | 100.00% | | | 100.00% | | | | | | | |
Collateral, voting capital stock, percent | 65.00% | | | 65.00% | | | 65.00% | | | | | | | |
Senior Notes | 6.00% And 6.375% Senior Secured Notes, Successor Notes | Peabody Investments (Gibraltar) Limited | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Collateral, non-voting capital stock, percent | 100.00% | | | 100.00% | | | 100.00% | | | | | | | |
Collateral, voting capital stock, percent | 65.00% | | | 65.00% | | | 65.00% | | | | | | | |
Senior Notes | Successor Credit Agreement | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Debt Instrument, Restricted Payments Basket | | | | | | | | | | | 650,000,000 | | | |
Debt Instrument, Restricted Payments Basket, Annual Limit | | | | | | | | | | | 150,000,000 | | | |
Aggregate consent payments | | | | | | | | | | | $ 19,800,000 | | | |
Other Expenses | | | | | | 1,500,000 | | | | | | | | |
Term Loan | Successor Credit Agreement | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Principal amount | $ 400,000,000 | | | $ 400,000,000 | | | $ 400,000,000 | | | | | | | |
Interest expense | 5,600,000 | 5,100,000 | | 17,000,000 | 18,500,000 | | | | | | | | | |
Debt Instrument, Restricted Payments Basket | | | | | | | | | | | | $ 450,000,000 | | |
Original issue discount and deferred finance costs | $ 37,300,000 | | | $ 37,300,000 | | | $ 37,300,000 | | | | | | | |
Debt Instrument, Principal Prepayment, Percent of Principal Amount if Repaid Before October 2018 | | | | | | | | | | 101.00% | | | | |
Mandatory principal prepayment, percent of excess cash flow | 75.00% | | | 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 | | | $ 10,000,000 | | | $ 10,000,000 | | | | | | | |
Repayments of Debt | | | $ 46,000,000 | | | | 556,000,000 | | | | | | | |
Payment for Debt Extinguishment or Debt Prepayment Cost | | | | | | | 546,000,000 | | | | | | | |
Restricted payments threshold | $ 450,000,000 | | | $ 450,000,000 | | | $ 450,000,000 | | | | | 50,000,000 | | |
Debt Instrument, Covenant, Fixed Charge Coverage Ratio | 2 | | | | | | | | | | | | | |
Term Loan | Successor Credit Agreement | Total Leverage Ratio Less or Equal to 2.00 to 1.00 Greater Than 1.50 to 1.00 | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Mandatory principal prepayment, percent of excess cash flow | 50.00% | | | 50.00% | | | 50.00% | | | | | | | |
Term Loan | Successor Credit Agreement | Total Leverage Ratio Less or Equal to 2.00 to 1.00 Greater Than 1.50 to 1.00 | Maximum | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Total Leverage Ratio | 2 | | | 2 | | | 2 | | | | | | | |
Term Loan | Successor Credit Agreement | Total Leverage Ratio Less or Equal to 2.00 to 1.00 Greater Than 1.50 to 1.00 | Minimum | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Total Leverage Ratio | 1.50 | | | 1.50 | | | 1.50 | | | | | | | |
Term Loan | Successor Credit Agreement | Total Leverage Ratio Less or Equal to 1.50 to 1.00 Greater Than 1.00 to 1.00 | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Mandatory principal prepayment, percent of excess cash flow | 25.00% | | | 25.00% | | | 25.00% | | | | | | | |
Term Loan | Successor Credit Agreement | Total Leverage Ratio Less or Equal to 1.50 to 1.00 Greater Than 1.00 to 1.00 | Maximum | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Total Leverage Ratio | 1.50 | | | 1.50 | | | 1.50 | | | | | | | |
Term Loan | Successor Credit Agreement | Total Leverage Ratio Less or Equal to 1.50 to 1.00 Greater Than 1.00 to 1.00 | Minimum | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Total Leverage Ratio | 1 | | | 1 | | | 1 | | | | | | | |
Term Loan | Successor Credit Agreement | Total Leverage Ratio Less or Equal to 1.00 to 1.00 | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Mandatory principal prepayment, percent of excess cash flow | 0.00% | | | 0.00% | | | 0.00% | | | | | | | |
Total Leverage Ratio | 1 | | | 1 | | | 1 | | | | | | | |
Term Loan | Successor Credit Agreement | Total Leverage Ration Less Or Equal 2.00 to 1.00 | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Total Leverage Ratio | 2 | | | 2 | | | 2 | | | | | | | |
Term Loan | Successor Credit Agreement | Total Leverage Ratio Less or Equal 1.25 to 1.00 | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Total Leverage Ratio | 1.25 | | | 1.25 | | | 1.25 | | | | | | | |
Dividend payment and stock purchase payment threshold | $ 25,000,000 | | | $ 25,000,000 | | | $ 25,000,000 | | | | | | | |
Term Loan | Successor Credit Agreement | London Interbank Offered Rate (LIBOR) | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Basis spread on variable rate | 2.75% | | | | | | | | | | | | | |
Term Loan | Successor Credit Agreement | Effect of Plan | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Principal amount | | | | | | | | | | | | | $ 950,000,000 | |
Term Loan | Senior Secured Term Loan due 2025, net of original issue discount | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Secured Debt | | | | | | | | | | | | | $ 950,000,000 | |
Long-term debt | $ 393,000,000 | | | 393,000,000 | | $ 395,900,000 | 393,000,000 | | | | | | | |
Line of Credit | 2017 Revolver | Revolving Credit Facility | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Long-term debt | | | | | | | | | | | | 350,000,000 | | |
Revolving Credit Facility | 2017 Revolver | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Debt issuance cost | 5,700,000 | | | 5,700,000 | | | 5,700,000 | | | | | 4,700,000 | | |
Interest expense | 1,400,000 | $ 1,300,000 | | 4,500,000 | $ 4,300,000 | | | | | | | | | |
Line of Credit Facility, Maximum Borrowing Capacity | 565,000,000 | | | 565,000,000 | | | 565,000,000 | | | | | $ 350,000,000 | | |
2019 Revolver commitments, matures 2023 | 540,000,000 | | | $ 540,000,000 | | | $ 540,000,000 | | | | | | | |
Unrestricted Cash Netting Limit | $ 800,000,000 | | | | | | | | | | | | | |
Debt Instrument, Base Interest Rate | 3.375% | | | 3.375% | | | 3.375% | | | | | | | |
Revolving Credit Facility, Fee on Unused Borrowings | 0.50% | | | 0.50% | | | 0.50% | | | | | | | |
Aggregate Letters of Credit, Maximum | $ 66,400,000 | | | $ 66,400,000 | | | $ 66,400,000 | | | | | | | |
Revolving Credit Facility | 2017 Revolver | Total Leverage Ration Less Or Equal 2.00 to 1.00 | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Total Leverage Ratio | 2 | | | 2 | | | 2 | | | | | | | |
Revolving Credit Facility | 2017 Revolver | London Interbank Offered Rate (LIBOR) | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
Basis spread on variable rate | 3.25% | | | | | | | | | | | | | |
Scenario, Forecast | Revolving Credit Facility | 2017 Revolver | | | | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | | | | |
2019 Revolver commitments, matures 2023 | | | | | | | | $ 540,000,000 | | | | | | |
2019 Revolver commitments, matures 2020 | | | | | | | | | $ 25,000,000 | | | | | |