Balance Sheet Components - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 21,557	$ 13,688
Less: Accumulated depreciation and amortization	(8,756)	(4,869)
Property and equipment, net	12,801	8,819
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,874	2,416
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	8,751	5,076
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,903	2,241
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	4,218	1,221
Construction in Process [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,811	$ 2,734

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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