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Selected Balance Sheet Components - Schedule of Deposits and Other Noncurrent Assets (Details) - USD ($)
$ in Thousands
Mar. 31, 2021
Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]    
Restricted cash and security deposit for the Irvine Lease (Note 14) $ 1,850 $ 1,850
Long-term prepaid maintenance contracts 97 118
Other 88 88
Total deposits and other noncurrent assets $ 2,035 $ 2,056