Benefit Plans Benefit Plans - Future Benefit Payments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Amount of net prior service credit	$ 0.0
Amount of net loss	5.6
Defined Benefit Plan, Amount to be Amortized from Accumulated Other Comprehensive Income (Loss) Next Fiscal Year [Abstract]
2017	52.0
2018	52.8
2019	53.9
2020	53.9
2021	53.8
2022-2026	276.5
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Amount of net prior service credit	0.0
Amount of net loss	0.1
Defined Benefit Plan, Amount to be Amortized from Accumulated Other Comprehensive Income (Loss) Next Fiscal Year [Abstract]
2017, gross	1.2
2018, gross	1.1
2019, gross	1.1
2020, gross	1.0
2021, gross	1.0
2022-2026, gross	4.2
2017, net	1.0
2018, net	1.0
2019, net	1.0
2020, net	0.9
2021, net	0.9
2022-2026, net	$ 3.8