Employee Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan Disclosure [Line Items]
Employer matching contributions	$ 9.5	$ 9.0	$ 8.6
Foreign Postretirement Benefit Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer matching contributions	$ 2.7	$ 2.7	$ 2.2