Redeemable Convertible Preferred Stock - Additional Information (Details)		1 Months Ended				3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 28, 2021 USD ($) shares	Mar. 31, 2021 USD ($) $ / shares shares	Feb. 28, 2021 USD ($) shares	Dec. 31, 2020 USD ($) shares	Jun. 30, 2020 USD ($) Tranche $ / shares shares	Mar. 31, 2021 USD ($) $ / shares	Jun. 30, 2020 USD ($) Tranche $ / shares shares	Sep. 30, 2021 USD ($) shares	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) shares
Redeemable Convertible Preferred Stock [Line Items]
Redeemable convertible preferred stock reclassified to equity	$ 260,500,000
Gross proceeds from issuance of convertible preferred stock								$ 165,521,000	$ 9,887,000
Series A Redeemable Convertible Preferred Stock
Redeemable Convertible Preferred Stock [Line Items]
Temporary equity, shares issued | shares				30,019,945	10,000,000		10,000,000	0		30,019,945
Preferred stock value, per share | $ / shares					$ 1.00		$ 1.00
Gross proceeds from issuance of convertible preferred stock					$ 10,000,000.0
Preferred stock shares issued upon conversion of outstanding convertible notes and accrued interest | shares					5,019,949
Preferred stock additional shares issued | shares					30,000,000		30,000,000
Minimum percentage of preferred stock milestone achievement approval or waiver					75.00%
Number of tranches | Tranche					2		2
Estimated fair value liability					$ 3,300,000
Stock issuance costs						$ 4,000	$ 177,000			$ 200,000
Series A Redeemable Convertible Preferred Stock | Tranche One
Redeemable Convertible Preferred Stock [Line Items]
Gross proceeds from issuance of convertible preferred stock					$ 15,000,000.0
Series A Redeemable Convertible Preferred Stock | Tranche Two
Redeemable Convertible Preferred Stock [Line Items]
Gross proceeds from issuance of convertible preferred stock				$ 15,000,000.0
Preferred stock additional shares issued | shares				15,000,000						15,000,000
Remeasured fair value liability upon settlement				$ 29,100,000
Series A Redeemable Convertible Preferred Stock | Tranche Three
Redeemable Convertible Preferred Stock [Line Items]
Gross proceeds from issuance of convertible preferred stock			$ 15,000,000.0
Preferred stock additional shares issued | shares			15,000,000
Stock issuance costs								$ 4,000
Remeasured fair value reported in current liability				$ 29,100,000						$ 29,100,000
Fair value, changes in fair value other loss			$ 10,300,000							$ 54,800,000
Remaining remeasured fair value liability			$ 39,400,000
Series B Redeemable Convertible Preferred Stock
Redeemable Convertible Preferred Stock [Line Items]
Conversion of stock | shares		29,792,487
Preferred stock value, per share | $ / shares		$ 5.06				$ 5.06
Gross proceeds from issuance of convertible preferred stock		$ 150,700,000
Stock issuance costs		$ 200,000				$ 226,000
Common Stock
Redeemable Convertible Preferred Stock [Line Items]
Conversion of stock | shares	30,761,676