License and Collaboration Agreements - License, Collaboration and Other Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 8,270	$ 6,208	$ 42,457	$ 102,948
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	0	0	28,000	90,000
Roche [Member] \| PEGASYS and MIRCERA [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	1,919	3,197	3,842	6,408
Daiichi Sankyo Europe GmbH [Member] \| ONZEALDTM (NKTR-102) [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	3,258	0	3,258	0
Amgen, Inc. [Member] \| Neulasta [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	1,250	1,250	2,500	2,500
Bayer Healthcare LLC [Member] \| BAY41-6551 (Amikacin Inhale) [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	357	395	714	1,205
Baxalta Incorporated [Member] \| ADYNOVATETM [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	207	88	313	197
Other [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 1,279	$ 1,278	$ 3,830	$ 2,638