Retirement Benefits (Details 14) $ in Millions	Dec. 31, 2017 USD ($)
Pension Benefits [Member]
Defined Benefit Plan Expected Future Benefit Payments [Abstract]
2018	$ 201.0
2019	194.1
2020	192.0
2021	188.8
2022	186.8
2023-2027	891.5
Other Postretirement Benefits [Member]
Defined Benefit Plan Expected Future Benefit Payments [Abstract]
2018	32.1
2019	31.2
2020	29.7
2021	28.1
2022	26.2
2023-2027	109.0
Medicare Part D Subsidy [Abstract]
2018	0.8
2019	0.8
2020	0.8
2021	0.7
2022	0.7
2023-2027	$ 2.8