Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Property and equipment	$ 20,643	$ 3,172
Less accumulated depreciation and amortization	(1,707)	(204)
Property and equipment, net	18,936	2,968
Furniture and office equipment
Property Plant And Equipment [Line Items]
Property and equipment	624	168
Computer equipment
Property Plant And Equipment [Line Items]
Property and equipment	77	67
Software
Property Plant And Equipment [Line Items]
Property and equipment	175	87
Leasehold improvements
Property Plant And Equipment [Line Items]
Property and equipment	11,568	64
Laboratory equipment
Property Plant And Equipment [Line Items]
Property and equipment	2,974	723
Manufacturing equipment
Property Plant And Equipment [Line Items]
Property and equipment	5,200	0
Construction in progress
Property Plant And Equipment [Line Items]
Property and equipment	$ 25	$ 2,063