Balance Sheet Components - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Property and equipment	$ 5,343	$ 4,824
Less: Accumulated depreciation and amortization	(2,336)	(2,080)
Property and equipment, net	3,007	2,744
Scientific Equipment
Property Plant And Equipment [Line Items]
Property and equipment	4,462	3,995
Furniture and Equipment
Property Plant And Equipment [Line Items]
Property and equipment	352	301
Capitalized Software
Property Plant And Equipment [Line Items]
Property and equipment	225	225
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment	$ 304	$ 303