Fair Value Measurements - Schedule of Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - Fair Value on a Recurring Basis - USD ($) $ in Thousands		Sep. 30, 2021	Dec. 31, 2020
Redeemable Convertible Preferred Stock Tranche Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities			$ 29,062
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	[1]	$ 394,804	19,782
Level 1 | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets	[1]	$ 394,804	19,782
Level 3 | Redeemable Convertible Preferred Stock Tranche Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities			$ 29,062

[1] Included within cash and cash equivalents on the condensed balance sheet.