Commitments and Contingencies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Obligations for base rent and CAM costs under facility and other non-cancelable operating leases
2019	$ 4,648
2020	3,140
Total minimum lease payments	7,788
Total rent and CAM expense	$ 4,000	$ 4,100	$ 4,800