Pension Plans and Other Post Employment Benefit Plans Weighted Average Assumptions used to Determine Net Periodic Benefit Cost - Pension (Details) - Pension Plan	4 Months Ended	8 Months Ended	12 Months Ended
	Dec. 31, 2017	Aug. 31, 2017	Dec. 31, 2018	Dec. 31, 2016
Successor [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Benefit, Discount Rate	3.42%		3.38%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	3.80%		4.04%
Expected long-term rate of return on plan assets	6.24%		6.19%
Successor [Member] | Principal U.S. Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Benefit, Discount Rate	3.73%		3.65%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	3.95%		4.25%
Expected long-term rate of return on plan assets	6.25%		6.25%
Predecessor [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Benefit, Discount Rate		3.80%		3.77%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase		3.80%		3.96%
Expected long-term rate of return on plan assets		7.66%		7.74%
Predecessor [Member] | Principal U.S. Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Benefit, Discount Rate		4.16%		4.04%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase		3.95%		4.15%
Expected long-term rate of return on plan assets		8.00%		8.00%