Balance Sheet Components - Components of Property and Equipment - Net (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 1,071	$ 776
Less: accumulated depreciation	(619)	(451)
Total property and equipment - net	452	325
Computer Equipment and Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	980	687
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	61	59
Furniture
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 30	$ 30

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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