BALANCE SHEET COMPONENTS - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 52,969	$ 52,563
Less: accumulated depreciation and amortization	(30,147)	(28,501)
Property and equipment, net	22,822	24,062
Prototype
Property Plant And Equipment [Line Items]
Property and equipment, gross	17,711	17,711
Machinery and Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	17,587	17,486
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	14,205	14,196
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,295	1,295
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	$ 782	$ 486

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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