License and Collaboration Agreements - License, Collaboration and Other Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 54	$ 27,515
Bristol-Myers Squibb Company | Bempegaldesleukin
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	0	25,000
Eli Lilly and Company | NKTR-358
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	0	1,259
Other
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 54	$ 1,256