Net Loss per Common Share - Anti-Dilutive Effect Excluded from Computation of Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded from computation of diluted net loss per share attributable to common stockholders	28,418,977	4,874,307
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded from computation of diluted net loss per share attributable to common stockholders	20,056,145	3,573,659
Unvested Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded from computation of diluted net loss per share attributable to common stockholders	554,724	1,044,516
Stock Options Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded from computation of diluted net loss per share attributable to common stockholders	3,530,706	168,296
Stock Options Available for Issuance
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded from computation of diluted net loss per share attributable to common stockholders	3,852,807	87,836
Employee Stock Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded from computation of diluted net loss per share attributable to common stockholders	424,595