Stock-Based Compensation - Stock based compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Stock based compensation expense
Total stock-based compensation expense	$ 2,242	$ 2,787	$ 4,870	$ 5,295
Research and development
Stock based compensation expense
Total stock-based compensation expense	728	1,056	1,496	2,014
General and administrative
Stock based compensation expense
Total stock-based compensation expense	$ 1,514	$ 1,731	$ 3,374	$ 3,281