License and Collaboration Agreements - License, Collaboration and Other Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 4,824	$ 8,270	$ 10,916	$ 42,457
AstraZeneca AB [Member] | MOVANTIK and MOVANTIK fixed-dose combination program [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	1,600	0	4,600	28,000
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	357	714	714
Daiichi Sankyo Europe GmbH [Member] | ONZEALDTM (NKTR-102) [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	216	3,258	431	3,258
Roche [Member] | MIRCERA [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	0	1,914	0	3,842
Baxalta Incorporated [Member] | ADYNOVATE [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	45	207	45	313
Other [Member]
License And Collaboration Agreements [Line Items]
License, collaboration and other revenue	$ 1,356	$ 1,284	$ 2,626	$ 3,830