Pensions - Additional Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
U.S. Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 2.7	$ 2.7
Estimated employer contributions in current year	6.9
Non-U.S. Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	0.7	$ 0.4
Estimated employer contributions in current year	$ 1.4