Stockholders' Equity - Summary of Stock-Based Compensation Expense (Details) - 2016 Equity Incentive Plans and Employee Stock Purchase Plan - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 2,107	$ 1,696	$ 5,944	$ 4,644
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	703	454	2,057	1,651
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 1,404	$ 1,242	$ 3,887	$ 2,993