Commitments and Contingencies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Leases [Abstract]
Operating Leases, Rent Expense	$ 15,325	$ 12,939	$ 11,166
Operating Leases, Future Minimum Payments, Due 2018	11,926
Operating Leases, Future Minimum Payments, Due 2019	7,760
Operating Leases, Future Minimum Payments, Due 2020	5,613
Operating Leases, Future Minimum Payments, Due 2021	4,890
Operating Leases, Future Minimum Payments, Due 2022	2,265
Operating Leases, Future Minimum Payments, Due Thereafter	$ 7,372