Balance Sheet Components - Summary of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Payables And Accruals [Abstract]
Accrued bonus and payroll expenses	$ 1,696	$ 1,476
Accrued professional and consulting services	153	490
Accrued clinical and manufacturing expenses	921	1,029
Accrued preclinical and research expenses	194	32
Other	307	401
Total accrued liabilities	$ 3,271	$ 3,428