Stock-Based Compensation - Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock-based compensation expense
Stock-based compensation expense	$ 8,953	$ 3,915	$ 4,551
Research and development
Stock-based compensation expense
Stock-based compensation expense	4,525	1,933	2,053
General and administrative
Stock-based compensation expense
Stock-based compensation expense	$ 4,428	$ 1,982	$ 2,498

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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