Balance Sheet Components - Summary of Property and Equipment Net (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property and equipment	$ 3,850	$ 4,103
Less: accumulated depreciation	(3,294)	(3,413)
Property and equipment, net	556	690
Research and Development Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	1,882	2,174
Furniture and Office Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	167	167
Computer Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	487	448
Software
Property Plant And Equipment [Line Items]
Total property and equipment	80	80
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	$ 1,234	$ 1,234