Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued liabilities
Accrued payroll-related expenses	$ 1,331	$ 1,045
Deferred licensing revenue		229
Deferred rent	230	248
Accrued sales commissions payable to sales representatives	75	193
Other	618	96
Total accrued liabilities	$ 2,254	$ 1,811