Retirement Benefits (Details 9) $ in Millions	Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit)	$ (2.5)
Amortization of net actuarial loss	76.5
Amortization of accumulated other comprehensive loss	74.0
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit)	0.4
Amortization of net actuarial loss	65.9
Amortization of accumulated other comprehensive loss	66.3
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service cost (credit)	(2.9)
Amortization of net actuarial loss	10.6
Amortization of accumulated other comprehensive loss	$ 7.7