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Pension and Savings Plans Textuals (Details) | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Apr. 01, 2017 USD ($) years plan | Dec. 31, 2017 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Predecessor |  |  |  |  |  |
Defined Contribution Plans [Abstract] |  |  |  |  |  |
Paid discretionary contributions to defined contribution pension plans, company match | $ 5,500,000 |  |  |  | $ (19,200,000) | $ (22,000,000)
Additional discretionary contributions to defined contribution pension plans, performance feature |  |  |  |  |  | $ (19,500,000)
Predecessor | Pension Plan [Member] |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Expected long-term return on plan assets | 5.90% |  |  |  | 6.00% | 6.25%
Defined Benefit Plan, Accumulated Benefit Obligation |  |  |  |  | $ 959,300,000 |
Defined Contribution Plans [Abstract] |  |  |  |  |  |
Pension obligations | $ 0 |  |  |  | $ 0 | $ 0
Predecessor | Equity Securities [Member] |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage |  |  |  |  | 31.00% |
Predecessor | Fixed Income Investments [Member] |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage |  |  |  |  | 69.00% |
Predecessor | Real Estate [Member] |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage |  |  |  |  | 2.00% |
Successor |  |  |  |  |  |
Defined Contribution Plans [Abstract] |  |  |  |  |  |
Number of 401(k) plans | plan | 2 |  |  |  |  |
Paid discretionary contributions to defined contribution pension plans, company match |  | $ 25,500,000 |  |  |  |
Successor | Pension Plan [Member] |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Retirees Affected by Pension Settlement |  | 1,950 |  |  |  |
Percentage of company's qualified pension plans on a GAAP accounting basis |  | 80.00% |  | 80.00% |  |
Expected long-term return on plan assets | 5.90% | 5.90% |  | 5.65% |  |
Percentage of actuarial gains and losses amortized | 5.00% |  |  |  |  |
Defined Benefit Plan, Amortization Period | years | 5 |  |  |  |  |
Defined Benefit Plan, Accumulated Benefit Obligation |  | $ 874,600,000 |  | $ 874,600,000 |  |
Payment for Pension and Other Postretirement Benefits |  | 30,100,000 |  |  |  |
Defined Contribution Plans [Abstract] |  |  |  |  |  |
Paid discretionary contributions to defined contribution pension plans, company match |  | 25,000,000 |  |  |  |
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement |  | 71,400,000 |  |  |  |
Pension obligations |  | $ 2,100,000 |  |  |  |
Successor | Equity Securities [Member] |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage |  | 27.00% |  | 27.00% |  |
Successor | Fixed Income Investments [Member] |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage |  |  |  |  | 73.00% |
Scenario, Forecast |  |  |  |  |  |
Defined Contribution Plans [Abstract] |  |  |  |  |  |
Additional discretionary contributions to defined contribution pension plans, performance feature |  |  | $ 9,500,000 |  |  |

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