Stock Based Compensation, Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Stock-Based Compensation Expense [Abstract]
Total share based compensation expense	$ 7,900	$ 3,961
Unrecognized share-based compensation cost	$ 55,700
Weighted average period expected to recognize unrecognized share-based compensation cost	3 years 3 days
Research and Development [Member]
Stock-Based Compensation Expense [Abstract]
Total share based compensation expense	$ 2,916	1,735
General and Administrative [Member]
Stock-Based Compensation Expense [Abstract]
Total share based compensation expense	4,984	2,226
Stock Options [Member]
Stock-Based Compensation Expense [Abstract]
Total share based compensation expense	7,826	3,961
Restricted Stock Units [Member]
Stock-Based Compensation Expense [Abstract]
Total share based compensation expense	$ 74	$ 0

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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