Balance Sheet Components - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 48,990	$ 45,802
Less: accumulated depreciation and amortization	(26,457)	(22,403)
Property and equipment, net	22,533	23,399
Prototype
Property Plant And Equipment [Line Items]
Property and equipment, gross	16,901	16,419
Machinery and Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	16,431	15,816
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	6,857	6,718
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,295	1,284
Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,389	1,389
Construction in Progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 6,117	$ 4,176

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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