Commitments and Contingencies - Future Minimum Lease Payments Under Operating and Capital Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Operating leases, 2019	$ 3,573
Operating leases, 2020	3,340
Operating leases, 2021	3,305
Operating leases, 2022	3,193
Operating leases, 2023	3,140
Operating leases, Thereafter	9,947
Operating leases, Total minimum lease payments	26,498
Capital leases, 2019	575
Capital leases, 2020	270
Capital leases, Total minimum lease payments	845
Less: Portion representing interest	(64)
Present value of capital lease obligations	781
Less: Current portion of capital lease obligations	(523)	$ (936)
Capital lease obligations, net of current portion	$ 258	$ 745