License and Collaboration Agreements - Summary of Revenues (Details) - Gilead and Taiho - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
License
License And Collaboration Agreements [Line Items]
License revenue	$ 55,096		$ 55,096
Collaboration
License And Collaboration Agreements [Line Items]
License revenue	9,434	$ 1,750	12,934	$ 5,250
Collaboration and License
License And Collaboration Agreements [Line Items]
License revenue	$ 64,530	$ 1,750	$ 68,030	$ 5,250