Redeemable Convertible Preferred Stock and Common Stock - Common Stock (Details)	Sep. 30, 2021 Vote $ / shares shares	Dec. 31, 2020 $ / shares shares
Common Stock Authorized (shares)	172,000,000	113,259,306
Common stock, par value (in dollars per share) | $ / shares	$ 0.0001	$ 0.0001
Number of votes | Vote	1
Shares of common stock reserved for issuance	19,185,183
2016 Stock Plan
Shares of common stock reserved for issuance	3,110,588	1,997,099