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, 2016	Dec. 31, 2015
Successor [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Benefit, Discount Rate	3.42%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	3.80%
Expected long-term rate of return on plan assets	6.24%
Successor [Member] | Principal U.S. Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Benefit, Discount Rate	3.73%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	3.95%
Expected long-term rate of return on plan assets	6.25%
Predecessor [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Benefit, Discount Rate		3.80%	3.77%	3.93%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase		3.80%	3.96%	4.01%
Expected long-term rate of return on plan assets		7.66%	7.74%	8.10%
Predecessor [Member] | Principal U.S. Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net Periodic Benefit, Discount Rate		4.16%	4.04%	4.29%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase		3.95%	4.15%	4.20%
Expected long-term rate of return on plan assets		8.00%	8.00%	8.50%