Redeemable Convertible Preferred Stock Warrant Liability - Schedule of Warrants to Purchase Shares of Redeemable Convertible Preferred Stock (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020	Jun. 30, 2017	Jul. 31, 2015
Class of Warrant or Right [Line Items]
Convertible preferred stock warrant liability	$ 0	$ 177,000
Series E, Redeemable Convertible Preferred Stock Warrants
Class of Warrant or Right [Line Items]
Exercise price of warrants (in dollars per share)				$ 13.73
Warrants outstanding (in shares)	0	72,000
Convertible preferred stock warrant liability	$ 0	$ 177,000	$ 763,000