Stock-Based Compensation - Summary of Stock Option Activity (Details) - 2002 Plan and 2018 Plan - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Total Options
Outstanding, beginning balance (in shares)	3,598,160	2,577,718
Granted (in shares)	1,271,836	1,227,159
Exercised (in shares)	(209,751)	(51,572)
Cancelled or expired (in shares)	(193,444)	(155,145)
Outstanding, ending balance (in shares)	4,466,801	3,598,160	2,577,718
Vested and expected to vest (in shares)	4,466,801
Vested and exercisable (in shares)	2,559,327
Weighted- Average Exercise Price Per Share
Outstanding, beginning balance (in usd per share)	$ 3.85	$ 3.29
Granted (in usd per share)	3.91	5.09
Exercised (in usd per share)	1.88	1.85
Cancelled or expired (in usd per share)	4.53	4.89
Outstanding, ending balance (in usd per share)	3.93	$ 3.85	$ 3.29
Vested and expected to vest (in usd per share)	3.93
Vested and exercisable (in usd per share)	$ 3.75
Weighted- Average Remaining Contractual Term (in years)
Outstanding (in years)	7 years 2 months 12 days	7 years 6 months	7 years 10 months 24 days
Vested and expected to vest (in years)	7 years 2 months 12 days
Vested and exercisable (in years)	6 years 2 months 12 days
Aggregate Intrinsic Value
Outstanding	$ 700,875	$ 1,737,432	$ 7,914,459
Vested and expected to vest	700,875
Vested and exercisable	$ 676,046