Pension Plans and Other Post Employment Benefit Plans Weighted Average Assumptions used to Determine Benefit Obligations and Periodic Benefit Cost - OPEB (Details) - Other Post Employment Benefits 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 Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net Periodic Benefit, Discount Rate	3.62%
Discount Rate	3.56%
Predecessor [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net Periodic Benefit, Discount Rate		4.03%	3.87%	4.13%
Discount Rate		3.62%	4.03%