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, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Discount Rate			3.63%
Weighted-average Discount Rate			3.61%
Interest Cost Discount Rate			3.26%
Rate of Increase in Future Compensation Levels			3.40%
Expected Long Term Rate of Return on Plan Assets			5.35%
Post-Freeze [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount Rate		3.94%		4.19%
Weighted-average Discount Rate		4.22%		4.15%
Interest Cost Discount Rate		3.18%		3.52%
Rate of Increase in Future Compensation Levels		3.15%		2.56%
Expected Long Term Rate of Return on Plan Assets		6.25%		5.80%
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%