Pension and Other Benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1.1	$ 1.5
Interest cost	8.6	9.2
Expected return on plan assets	(8.5)	(8.5)
Amortization of prior service cost	0.0	0.0
Amortization of actuarial losses	2.8	2.8
NET PERIODIC BENEFIT COST	4.0	5.0
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.0	0.0
Interest cost	0.2	0.3
Expected return on plan assets	0.0	0.0
Amortization of prior service cost	(0.2)	(0.2)
Amortization of actuarial losses	0.0	0.0
NET PERIODIC BENEFIT COST	$ 0.0	$ 0.1