License and Collaboration Agreements - License, Collaboration and Other Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 165,604	$ 153,289	$ 80,872
AstraZeneca AB [Member] | MOVANTIKTM (NKTR-118) and MOVANTIKTM fixed-dose combination program (NKTR-119) [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	130,000	105,001	25,016
Roche [Member] | PEGASYS and MIRCERA [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	12,816	12,845	18,382
Baxalta Incorporated [Member] | ADYNOVATETM [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	10,694	10,258	1,702
Amgen, Inc. [Member] | Neulasta [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	5,000	5,000	5,035
Bayer Healthcare LLC [Member] | BAY41-6551 (Amikacin Inhale) [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	1,919	4,717	15,293
Affymax, Inc. [Member] | OMONTYS [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	0	0	7,149
Other [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 5,175	$ 15,468	$ 8,295