Stock-Based Compensation - Accounting for Stock-based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	$ 545	$ 1,111
Research and development
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	95	380
Research and development | Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	6	12
Research and development | Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	89	368
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	450	731
General and administrative | Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	2	2
General and administrative | Equity Incentive Plans
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation	$ 448	$ 729