Commitments and Contingencies - Future Minimum Annual Lease Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Operating leases 2018	$ 1,679
Operating leases 2019	1,583
Operating leases 2020	1,624
Operating leases 2021	993
Total Operating leases	5,879
Capital leases 2018	105
Capital leases 2019	37
Capital leases 2020	37
Capital leases 2021	37
Capital leases 2022	37
Total Capital leases	253
Less: amount representing interest	(31)
Present value of minimum lease payments	222	$ 480
Current portion of capital leases	(93)
Capital leases, less current portion	$ 129