Employee Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
United States Employees, Defined Contribution [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Contributions to defined contribution plans	$ 5.2	$ 5.2	$ 4.8
International Employees, Defined Contribution [Member]
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Contributions to defined contribution plans	$ 0.1	$ 0.1	$ 0.1