Equity Incentive Plans and Stock-Based Compensation - Summary of Components and Classification of Stock-based Compensation Expense for Stock-based Awards (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 1,169	$ 480	$ 2,380	$ 1,298
Restricted Stock Awards and Founders' Common Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	51	118	160	262
Stock Options And ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	1,118	362	2,220	1,036
Research and Development Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	564	198	1,015	423
General and Administrative Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 605	$ 282	$ 1,365	$ 875