Employee Benefit Plans (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed			5.90%
Ultimate trend rate			4.50%
Effect of one percentage point increase on postretirement benefit obligation			$ 8.5
Effect of one percentage point increase on postretirement benefit cost			$ 0.4
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations (percent)			35.00%
Fixed income securities
Defined Benefit Plan Disclosure [Line Items]
Target plan asset allocations (percent)			65.00%
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation of pension plans			$ 228.9	$ 270.1
Pension contributions planned for next fiscal year			0.4
Other postretirement benefits payments	$ 3.5		17.9	$ 18.0
Pension Benefits | Predecessor
Defined Benefit Plan Disclosure [Line Items]
Other postretirement benefits payments		$ 13.8
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Gains amortized from accumulated other comprhensive income into net periodic benefit cost, next fiscal year			$ 3.0