Employee Benefit Plans - Schedule of Components of Period Benefit Costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Interest cost of projected benefit obligations	$ 1.3	$ 1.3	$ 2.6	$ 2.6
Expected return on assets	(1.3)	(1.5)	(2.8)	(3.0)
Amortization of actuarial net loss	0.5	0.5	1.1	1.0
Net periodic benefit cost	0.5	0.3	0.9	0.6
Postretirement Health and Other Plans
Defined Benefit Plan Disclosure [Line Items]
Interest cost of projected benefit obligations	0.1	0.0	0.2	0.1
Expected return on assets	0.0	0.0	0.0	0.0
Amortization of actuarial net loss	0.1	0.0	0.1	0.0
Net periodic benefit cost	$ 0.2	$ 0.0	$ 0.3	$ 0.1