Debt - Convertible Notes - Additional Information (Details) - USD ($)		1 Months Ended		3 Months Ended		9 Months Ended
	Sep. 03, 2021	May 31, 2020	Dec. 31, 2019	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Nov. 30, 2019	May 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt				$ (16,853,000)		$ (16,853,000)
Amortization of debt premium and discount				400,000	$ 500,000	1,400,000	$ 900,000
Interest expense				$ 3,611,000	3,293,000	$ 10,663,000	8,714,000
Second Lien Loan and Security Agreements
Debt Instrument [Line Items]
Amount borrowed			$ 21,000,000.0					$ 15,000,000.0			$ 29,200,000
2018 Note Agreements
Debt Instrument [Line Items]
Convertible notes											$ 10,000,000.0
Accrue interest fixed rate				8.00%		8.00%
2018 Note Agreements | Maximum
Debt Instrument [Line Items]
Convertible notes												$ 20,000,000.0
2019 Note Agreements
Debt Instrument [Line Items]
Accrue interest fixed rate				8.00%		8.00%
2019 Note Agreements | Maximum
Debt Instrument [Line Items]
Convertible notes									$ 10,500,000	$ 10,500,000
Amendment
Debt Instrument [Line Items]
Debt instrument extended maturity period			2023-06
Amendment | Other Income (Expense)
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt			$ (7,700,000)
Amendment | Additional Paid-in Capital
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt			$ 1,800,000
2020 Note Agreement
Debt Instrument [Line Items]
Debt instrument, maturity date		Jun. 30, 2023
Accrue interest fixed rate				8.00%		8.00%
Deferred payment obligations additional amount to be drawn retained				$ 15,000,000.0		$ 15,000,000.0
2020 Note Agreement | Maximum
Debt Instrument [Line Items]
Convertible notes		$ 30,000,000.0
Amended 2018 Note Agreements, 2019 Note Agreements, and 2020 Note Agreement
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt				(16,900,000)		$ (16,900,000)
Debt instrument, maturity date	Dec. 31, 2026
Debt instrument, convertible, terms of conversion feature						to automatically convert all principal and interest owing on our outstanding convertible promissory notes into shares of common stock if either (i) the offering price per share of our IPO is greater than $5.61 and the aggregate gross proceeds to the Company from the IPO are greater than $50.0 million or (ii) the Company receives a written request from the holders of at least 66 2/3% of the redeemable convertible preferred stock to convert all outstanding redeemable convertible preferred stock to common stock.
Amended 2018 Note Agreements, 2019 Note Agreements, and 2020 Note Agreement | Minimum
Debt Instrument [Line Items]
Offering price per share	$ 5.61
Gross proceeds from offering	$ 50,000,000.0
Convertible Note
Debt Instrument [Line Items]
Estimated fair value of aggregate outstanding derivative instrument				20,600,000		$ 20,600,000		33,500,000
Accrued interest				463,000		463,000		$ 5,134,000
Notes
Debt Instrument [Line Items]
Interest expense				1,900,000	$ 1,900,000	5,900,000	$ 4,600,000
Accrued interest				$ 500,000		$ 500,000