Employee Retirement Benefit Plans (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Retirement Benefit Plans (Textual) [Abstract]
Maximum employee annual contributions, percent	100.00%
US Based Employees
Employee Retirement Benefit Plans (Textual) [Abstract]
Total contributions under plans	$ 10.4	$ 9.9	$ 9.7
Non US Based Employees
Employee Retirement Benefit Plans (Textual) [Abstract]
Total contributions under plans	$ 4.5	$ 3.9	$ 3.7