License and Collaboration Agreements - Additional Information (Detail) - USD ($)		1 Months Ended									3 Months Ended				12 Months Ended
	Sep. 16, 2014	Nov. 30, 2015	Aug. 31, 2015	Oct. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Nov. 30, 2013	Jun. 30, 2013	Feb. 29, 2012	Dec. 31, 2009	Mar. 31, 2015	Dec. 31, 2013	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2007	Jul. 31, 2016	Jul. 31, 2015
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones															$ 113,300,000
AstraZeneca AB [Member] | United States [Member]
Deferred Revenue Arrangement [Line Items]
Liability to AZ for DTC advertising payments											$ 10,000,000									$ 5,000,000
Reduction of revenue											(10,000,000)
AstraZeneca AB [Member] | Scenario, Forecast [Member] | United States [Member] | Other Current Liabilities [Member]
Deferred Revenue Arrangement [Line Items]
Liability to AZ for DTC advertising payments																			$ 5,000,000
AstraZeneca AB [Member] | MOVANTIKTM (NKTR-118) and MOVANTIKTM fixed-dose combination program (NKTR-119) [Member] | Upfront Payment Arrangement in 2007 [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]
Contingent payments receivable based on development events regulatory to be pursued and completed solely by others															75,000,000
AstraZeneca AB [Member] | MOVANTIK [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments				$ 35,000,000			$ 70,000,000				$ 100,000,000
Deferred revenue															0
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%
AstraZeneca AB [Member] | MOVANTIK [Member] | European Union [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments			$ 40,000,000
Baxalta Incorporated [Member] | ADYNOVATETM (Hemophilia) [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue															0
Development milestones achieved		$ 10,000,000			$ 8,000,000
Baxalta Incorporated [Member] | ADYNOVATETM (Hemophilia) [Member] | European Union [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones															10,000,000
Roche [Member] | License Extension Option [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments										$ 31,000,000
Roche [Member] | PEGASYS [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue															0
Roche [Member] | MIRCERA [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue															5,400,000
Consideration received for product delivered in 2013									$ 27,000,000			$ 18,600,000
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 in 2007 [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments									$ 5,000,000
Roche [Member] | PEGASYS and MIRCERA [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue															2,300,000
Amgen, Inc. [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments													$ 50,000,000
Deferred revenue															24,200,000
Bayer Healthcare LLC [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones															50,000,000
Deferred revenue															19,300,000
Payment made to Bayer for cost of Phase 3 clinical trial								$ 10,000,000
Bayer Healthcare LLC [Member] | Performance-based Milestone Payments [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments															30,000,000
Development milestone achieved in 2013																	$ 10,000,000
Bayer Healthcare LLC [Member] | Upfront Payment Arrangement in 2007 [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments																		$ 40,000,000
Ophthotech Corporation [Member] | Fovista [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones															9,500,000
Received upfront and milestone payments						$ 19,800,000
Deferred revenue															18,200,000
Potential future development milestones upon acceptance for review of regulatory approval															2,500,000
Affymax, Inc. [Member] | OMONTYS [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue recognized																	$ 6,700,000
Other [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones															46,800,000
Deferred revenue															$ 14,500,000
Development milestones achieved																$ 9,000,000