Balance Sheet Components - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Property and equipment	$ 10,028	$ 7,608
Less: Accumulated depreciation	(5,145)	(4,461)
Property and equipment, net	4,883	3,147
Scientific Equipment
Property Plant And Equipment [Line Items]
Property and equipment	8,160	5,935
Furniture and Equipment
Property Plant And Equipment [Line Items]
Property and equipment	1,172	1,064
Capitalized Software
Property Plant And Equipment [Line Items]
Property and equipment	278	278
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment	$ 418	$ 331

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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