Commitments and Contingencies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) individual	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Loss Contingency [Abstract]
Loss Contingency Accrual	$ 5,300		$ 8,600
Deferred Compensation Arrangement with Individual, Number of Individuals with Benefits | individual	3
Supplemental Unemployment Benefits, Severance Benefits	$ 8,500
Operating Leases, Rent Expense	20,900	$ 20,300	$ 22,200
Operating Leases, Future Minimum Payments Due [Abstract]
Operating Leases, Future Minimum Payments Due, Current	15,077
Operating Leases, Future Minimum Payments, Due in Two Years	10,732
Operating Leases, Future Minimum Payments, Due in Three Years	8,233
Operating Leases, Future Minimum Payments, Due in Four Years	5,997
Operating Leases, Future Minimum Payments, Due in Five Years	4,974
Operating Leases, Future Minimum Payments, Due Thereafter	16,247
Operating Leases, Future Minimum Payments Due	$ 61,260