License and Collaboration Agreements - Summary of Revenues by Collaboration and by Category of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
License And Collaboration Agreements [Line Items]
Total revenues	$ 9,461	$ 64,530	$ 28,383	$ 68,030
Gilead License To Zimberelimab
License And Collaboration Agreements [Line Items]
Total revenues		55,096		55,096
Gilead Access Rights
License And Collaboration Agreements [Line Items]
Total revenues	7,711	7,684	23,133	7,684
Taiho Collaboration Agreement
License And Collaboration Agreements [Line Items]
Total revenues	$ 1,750	$ 1,750	$ 5,250	$ 5,250