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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