Stock Based Compensation - Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	18 Months Ended
Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2022
Stock Based Compensation
Stock based compensation	$ 1,731	$ 1,986	$ 3,349	$ 3,690
Unrecognized stock-based compensation expense	14,000		$ 14,000	14,000
Period of unrecognized stock-based compensation expense			2 years 4 months 24 days
Research and development
Stock Based Compensation
Stock based compensation	549	871	$ 1,064	1,710
General and administrative
Stock Based Compensation
Stock based compensation	$ 1,182	$ 1,115	$ 2,285	$ 1,980

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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