Stock-Based Compensation - Stock Option Activity (Details) - Stock Options - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Shares
Options outstanding at beginning of the period (in shares)	3,042,229
Granted (in shares)	1,350,210
Exercised (in shares)	(192,464)
Canceled (in shares)	(70,349)
Options outstanding at the end of the period (in shares)	4,129,626	3,042,229
Options vested and expected to vest at the end of the period (in shares)	3,982,965
Options exercisable at the end of the period (in shares)	1,387,147
Shares available for grant under the 2021 Plan	3,319,116
Weighted Average Exercise Price Per Share
Options outstanding at beginning of the period (in dollars per share)	$ 28.93
Granted (in dollars per share)	28.16
Exercised (in dollars per share)	9.53
Canceled (in dollars per share)	35.62
Options outstanding at the end of the period (in dollars per share)	29.46	$ 28.93
Options vested and expected to Vest at the end of the period (in dollars per share)	29.81
Options exercisable at the end of the period (in dollars per share)	$ 51.75
Weighted Average Remaining Contractual Term (In Years)
Options outstanding at the end of the period	8 years 2 months 12 days	8 years 2 months 12 days
Options vested and expected to vest at the end of the period	8 years 2 months 12 days
Options exercisable at the end of the period	6 years 8 months 12 days