Condensed Consolidated Balance Sheet Components - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Total	$ 18,458	$ 15,208
Less: Accumulated depreciation and amortization	(6,696)	(3,978)
Property and equipment, net	11,762	11,230	[1]
Scientific Equipment
Property Plant And Equipment [Line Items]
Total	6,459	5,053
Furniture and Equipment
Property Plant And Equipment [Line Items]
Total	771	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	$ 254	$ 119

[1] The Condensed Consolidated Balance Sheet as of December 31, 2017 has been derived from the audited financial statements as of that date.