Pensions - Summary of Components of Net Postretirement Pension Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
U.S. Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0.0	$ 0.0
Interest cost	1.6	1.9
Amortization of actuarial loss	(0.8)	(0.6)
Expected return on plan assets	(2.2)	(2.4)
Net postretirement pension expense	0.2	0.1
Non-U.S. Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.1	0.0
Interest cost	0.3	0.3
Amortization of actuarial loss	(0.2)	(0.2)
Expected return on plan assets	(0.6)	(0.5)
Net postretirement pension expense	$ 0.0	$ 0.0