License and Collaboration Agreements - Summary of Revenues by Collaboration and by Category of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
License And Collaboration Agreements [Line Items]
Collaboration and license revenue	$ 9,461	$ 1,750	$ 18,922	$ 3,500
Gilead Access Rights
License And Collaboration Agreements [Line Items]
Collaboration and license revenue	7,711		15,422
Taiho Collaboration Agreement
License And Collaboration Agreements [Line Items]
Collaboration and license revenue	$ 1,750	$ 1,750	$ 3,500	$ 3,500