Balance Sheet Components - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 7,565	$ 5,643
Less: accumulated depreciation and amortization	(2,017)	(1,657)
Property and equipment, net	5,548	3,986
Lab Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	3,306	3,011
Computer and Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,037	959
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	308	306
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	676	669
Construction in Progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 2,238	$ 698