Pension Benefits - Actuarial Assumptions Pension Expense (Details) - Pension Plans, Defined Benefit [Member]	4 Months Ended	8 Months Ended	12 Months Ended
	May 12, 2016	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Discount Rate			4.19%	4.10%
Weighted-average Discount Rate			4.15%	0.00%
Interest Cost Discount Rate			3.52%	0.00%
Rate of Increase in Future Compensation Levels			2.56%	3.31%
Expected Long Term Rate of Return on Plan Assets			5.80%	6.75%
Post-Freeze [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount Rate		3.94%
Weighted-average Discount Rate		4.22%
Interest Cost Discount Rate		3.18%
Rate of Increase in Future Compensation Levels		3.15%
Expected Long Term Rate of Return on Plan Assets		6.25%
Pre-Freeze [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.47%
Weighted-average Discount Rate	4.78%
Interest Cost Discount Rate	3.69%
Rate of Increase in Future Compensation Levels	3.15%
Expected Long Term Rate of Return on Plan Assets	6.25%