Balance Sheet Components - Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 9,060	$ 8,676
Less: Accumulated depreciation	(8,457)	(8,161)
Property and equipment, net	603	515
Depreciation	296	312
Machinery, equipment, furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,742	3,544
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,916	2,730
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,402	$ 2,402

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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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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