Commitments and Contingencies - Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Operating Leases, Rent Expense	$ 7,200	$ 6,400	$ 5,600
Future Operating Lease Minimum Payments, Due Next Year	7,068
Future Operating Lease Minimum Payments, Due in Two Years	5,635
Future Operating Lease Minimum Payments, Due in Three Years	4,509
Future Operating Lease Minimum Payments, Due in Four Years	3,523
Future Operating Lease Minimum Payments, Due in Five Years	2,659
Future Operating Lease Minimum Payments, Due Therafter	$ 7,779