Commitments and Contingencies - Additional Information (Details)	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2021 USD ($)	Sep. 30, 2021 USD ($) ft² LeaseFacility	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) ft² LeaseFacility	Sep. 30, 2020 USD ($)	Feb. 28, 2019 $ / shares shares
Operating Leased Assets [Line Items]
Redeemable convertible preferred stock, shares authorized | shares						18,992,220
Redeemable convertible preferred stock, shares issued | shares						18,992,220
Redeemable convertible preferred stock, par value per share | $ / shares						$ 0.0001
Redeemable convertible preferred stock, purchase price per share | $ / shares						$ 3.4225
Change in fair value of redeemable convertible preferred stock tranche liability			$ 8,364,000		$ 9,533,000
Number of lease facility | LeaseFacility		5		5
Aggregate sublease income to be earned				$ 67,600,000
Letter of credit outstanding		$ 1,800,000		1,800,000
Operating leases rent expense		2,400,000	100,000	6,400,000	400,000
Operating leases variable lease payments		500,000		1,700,000	200,000
Seattle Sublease
Operating Leased Assets [Line Items]
Sublease agreement term	2021-06
Sublease commencement date	Jul. 01, 2021
Sublease period	58 months
Aggregate estimated base rent payments	$ 5,500,000
Letter of credit outstanding		$ 300,000		$ 300,000
Sublease | C A
Operating Leased Assets [Line Items]
Total square footage of leased property | ft²		110,000		110,000
Sublease Income		$ 1,700,000	0	$ 4,400,000	0
Maximum
Operating Leased Assets [Line Items]
Change in fair value of redeemable convertible preferred stock tranche liability			8,400,000		$ 9,500,000
Operating lease, remaining lease term		9 years		9 years
Operating leases variable lease payments			$ 100,000
Minimum
Operating Leased Assets [Line Items]
Operating lease, remaining lease term		3 months		3 months