Summary of Significant Accounting Policies (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue	[1]	$ 25	$ 3	$ 117	$ 36,297
Net loss		$ (50,853)	$ (70,254)	$ (181,702)	$ (174,721)
Net loss per common share, basic (in dollars per share)		$ (0.20)	$ (0.28)	$ (0.73)	$ (0.71)
Net loss per common share, diluted (in dollars per share)		$ (0.20)	$ (0.28)	$ (0.73)	$ (0.71)
GSK | GSK Agreement | Change in Collaboration and License Agreement estimate
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue					$ 35,300
Net loss					$ 35,300
Net loss per common share, basic (in dollars per share)					$ 0.14
Net loss per common share, diluted (in dollars per share)					$ 0.14

[1] (1)    Including related-party revenue of zero for both the three months ended September 30, 2023 and 2022, and zero and $36,299 for the nine months ended September 30, 2023 and 2022, respectively.