Stockholders' Equity - Stock Options - Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Number of shares
Outstanding at beginning of period (in shares)	1,008,648
Granted (in shares)	72,063
Exercised (in shares)	(112,819)
Canceled (in shares)	(15,366)
Outstanding at end of period (in shares)	952,526	1,008,648
Weighted-average exercise price
Outstanding at beginning of period (in dollars per share)	$ 23.92
Granted (in dollars per share)	94.76
Exercised (in dollars per share)	16.38
Canceled (in dollars per share)	84.78
Outstanding at end of period (in dollars per share)	$ 29.19	$ 23.92
Additional disclosures
Weighted average remaining contractual term	7 years 9 months 18 days	8 years 5 months 4 days
Aggregate intrinsic value	$ 50,981	$ 66,028
Vested and Exercisable
Vested and exercisable, number (in shares)	610,568
Vested and exercisable, weighted average exercise price (in dollars per share)	$ 18.58
Vested and exercisable, weighted average remaining contractual term	7 years 7 months 2 days
Vested and exercisable, aggregate intrinsic value	$ 38,171