Redeemable Convertible Preferred Stock (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) ownershipClass	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Temporary Equity [Line Items]
Number of ownership classes | ownershipClass	2
Unpaid cumulative distributions included in accrued expenses-related party	$ 5,082	$ 0
Redeemable convertible preferred stock	0	0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Redeemable convertible preferred stock tranche obligation	2,832	$ 0
Previously Reported
Temporary Equity [Line Items]
Redeemable convertible preferred stock	$ 17,560							$ 17,560
Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Distribution priority, rate	1.5
Preferred returns, annual rate	8.00%
Unpaid cumulative distributions included in accrued expenses-related party	$ 4,800
Liquidation preference	37,114
Redeemable convertible preferred stock tranche obligation	2,832
Redeemable Convertible Preferred Stock | Previously Reported
Temporary Equity [Line Items]
Redeemable convertible preferred stock	$ 17,560