Pensions - Summary of Components of Net Postretirement Pension Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
U.S. Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0.0	$ 0.0	$ 0.0	$ 0.0
Interest cost	1.6	1.9	3.2	3.8
Amortization of actuarial loss	0.7	0.6	1.5	1.2
Expected return on plan assets	(2.2)	(2.4)	(4.4)	(4.8)
Net postretirement pension expense (benefit)	0.1	0.1	0.3	0.2
Non-U.S. Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.0	0.1	0.1	0.1
Interest cost	0.4	0.4	0.7	0.7
Amortization of actuarial loss	0.1	0.1	0.3	0.3
Expected return on plan assets	(0.6)	(0.5)	(1.2)	(1.0)
Net postretirement pension expense (benefit)	$ (0.1)	$ 0.1	$ (0.1)	$ 0.1