License and Collaboration Agreements - License, Collaboration and Other Revenue (Detail) - 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]
Total license, collaboration and other revenue	$ 28	$ 26,275	$ 82	$ 53,790
Bristol-Myers Squibb Company | Bempegaldesleukin
License And Collaboration Agreements [Line Items]
Total license, collaboration and other revenue	0	25,000	0	50,000
Eli Lilly and Company | NKTR-358
License And Collaboration Agreements [Line Items]
Total license, collaboration and other revenue	0	0	0	1,259
Other
License And Collaboration Agreements [Line Items]
Total license, collaboration and other revenue	$ 28	$ 1,275	$ 82	$ 2,531