Consolidated Balance Sheet Components - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Total	$ 18,750	$ 15,208
Less: Accumulated depreciation and amortization	(7,643)	(3,978)
Property and equipment, net	11,107	11,230
Scientific Equipment
Property Plant And Equipment [Line Items]
Total	6,628	5,053
Furniture and Equipment
Property Plant And Equipment [Line Items]
Total	813	625
Capitalized Software
Property Plant And Equipment [Line Items]
Total	146	131
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total	10,828	9,280
Construction in Progress
Property Plant And Equipment [Line Items]
Total	$ 335	$ 119