Notes Payable - Schedule of Aggregate Carrying Amounts of Term Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Less: unamortized discount	$ (154)
Total	10,123
Line of Credit
Debt Instrument [Line Items]
Principal	10,000	$ 10,000
Add: accreted liability for Final Payment fee	277	176
Less: unamortized discount	(154)	(235)
Total	$ 10,123	$ 9,941