License and Collaboration Agreements - Additional Information (Detail) - USD ($)					1 Months Ended							3 Months Ended			12 Months Ended
	Sep. 21, 2016	May 30, 2016	Mar. 01, 2016	Sep. 16, 2014	Jan. 31, 2017	Aug. 31, 2016	Mar. 31, 2016	Nov. 30, 2015	Jun. 30, 2014	Jun. 30, 2013	Feb. 29, 2012	Mar. 31, 2017	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2013	Dec. 31, 2007	Dec. 31, 2016
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones												$ 147,000,000
Liability for refundable upfront payment												12,500,000					$ 12,500,000
AstraZeneca-Kirin [Member]
Deferred Revenue Arrangement [Line Items]
Percentage of upfront payment, market access milestones, royalties and sales milestones			40.00%
ONZEALDTM (NKTR-102) [Member] | Turkey [Member]
Deferred Revenue Arrangement [Line Items]
Percentage of royalty on net sales		15.00%
AstraZeneca AB [Member] | MOVANTIK and MOVANTIK fixed-dose combination program [Member] | Upfront Payment Arrangement [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments														$ 125,000,000
AstraZeneca AB [Member] | MOVANTIK Fixed-dose Combination Program [Member]
Deferred Revenue Arrangement [Line Items]
Potential contingent payments based on development events												75,000,000
AstraZeneca AB [Member] | AstraZeneca-Kirin [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments							$ 28,000,000					3,000,000
Upfront and milestone payments received by Our collaboration partner under sublicense arrangement			$ 70,000,000
Percentage of upfront milestones royalty and sales milestone payments from sublicense agreement retained by our collaboration partner			60.00%
Deferred revenue												0
AstraZeneca AB [Member] | MOVANTIK [Member]
Deferred Revenue Arrangement [Line Items]
Percentage of post approval study costs to repay				33.00%
Maximum potential reduction in royalties				$ 35,000,000
AstraZeneca AB [Member] | MOVANTIK [Member] | United States [Member]
Deferred Revenue Arrangement [Line Items]
Potential reduction in U.S. royalty rate for repayment				2.00%
Daiichi Sankyo Europe GmbH [Member] | ONZEALDTM (NKTR-102) [Member]
Deferred Revenue Arrangement [Line Items]
Eligible milestone payments receivable upon achievement of regulatory and commercial milestones												60,000,000
Milestone payments to be received upon first commercial sales												10,000,000
Milestone payment to be received upon first commercial sale after final regulatory approval												25,000,000
Milestone payments to be received upon first achievement of annual net sales target												25,000,000
Liability for refundable upfront payment												12,500,000					$ 12,500,000
Daiichi Sankyo Europe GmbH [Member] | ONZEALDTM (NKTR-102) [Member] | European Territory Except Turkey [Member]
Deferred Revenue Arrangement [Line Items]
Percentage of royalty on net sales		20.00%
Daiichi Sankyo Europe GmbH [Member] | ONZEALDTM (NKTR-102) [Member] | Upfront Payment Arrangement [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments						$ 20,000,000
Deferred revenue												3,600,000
Non-refundable portion of upfront payment		$ 7,500,000
Revenue recognized from upfront payment												3,900,000
Baxalta Incorporated [Member] | ADYNOVATE (Hemophilia) [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue												0
Development milestones achieved								$ 10,000,000
Baxalta Incorporated [Member] | ADYNOVATE (Hemophilia) [Member] | European Union [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones												10,000,000
Roche [Member] | MIRCERA [Member] | Performance-based Milestone Payments [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments											$ 22,000,000
Roche [Member] | MIRCERA [Member] | Upfront Payment Arrangement [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments											$ 5,000,000
Amgen, Inc. [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments													$ 50,000,000
Deferred revenue												17,900,000
Bayer Healthcare LLC [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones												50,000,000
Deferred revenue												17,500,000
Payment made to Bayer for cost of Phase 3 clinical trial										$ 10,000,000
Potential future development milestones related to FDA approval												22,500,000
Bayer Healthcare LLC [Member] | Performance-based Milestone Payments [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments															$ 30,000,000
Bayer Healthcare LLC [Member] | Upfront Payment Arrangement [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments																$ 40,000,000
Ophthotech Corporation [Member]
Deferred Revenue Arrangement [Line Items]
Advances from collaboration partner payment					$ 12,700,000
Ophthotech Corporation [Member] | Reagent Shipments [Member]
Deferred Revenue Arrangement [Line Items]
Advances from collaboration partner payment					10,400,000
Ophthotech Corporation [Member] | Minimum Purchase Requirement [Member]
Deferred Revenue Arrangement [Line Items]
Advances from collaboration partner payment					$ 2,300,000
Ophthotech Corporation [Member] | Fovista [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments									$ 19,800,000
Deferred revenue												$ 16,500,000
Bristol-Myers Squibb [Member] | NKTR-214 [Member]
Deferred Revenue Arrangement [Line Items]
Percentage of out-of-pocket costs reimbursed by partner	50.00%
License agreement exclusivity expiration date												Sep. 30, 2018
License agreement exclusivity negotiation period												3 months
Other [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones												$ 45,500,000
Deferred revenue												$ 7,700,000