License and Collaboration Agreements - License, Collaboration and Other Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 436	$ 55,849	$ 16,975
Bristol-Myers Squibb | Bempegaldesleukin
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	0	50,000	0
Eli Lilly and Company | NKTR-358
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	0	1,259	7,019
Amgen, Inc. | Neulasta
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	0	4,167	5,000
Other
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 436	$ 423	$ 4,956