Consideration received for product delivered.

No definition available.

Name:	nktr_ConsiderationReceivedForProductDelivered
Namespace Prefix:	nktr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Contingent payments receivable based on development events.

+ References

No definition available.

+ Details

Name:	nktr_ContingentPaymentsReceivableBasedOnDevelopmentEvents
Namespace Prefix:	nktr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Increase Decrease In Revenue

+ References

No definition available.

+ Details

Name:	nktr_IncreaseDecreaseInRevenue
Namespace Prefix:	nktr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Liability to AZ for DTC advertising payments.

+ References

No definition available.

+ Details

Name:	nktr_LiabilitiesToPartnersForDirectConsumerAdvertisingPayments
Namespace Prefix:	nktr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Payment made to Bayer for cost of Phase 3 clinical trial.

+ References

No definition available.

+ Details

Name:	nktr_PaymentForReimbursementOfCosts
Namespace Prefix:	nktr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of post approval study costs to repay.

+ References

No definition available.

+ Details

Name:	nktr_PercentageOfPostApprovalStudyCostsToRepay
Namespace Prefix:	nktr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Potential development milestones.

+ References

No definition available.

+ Details

Name:	nktr_PotentialDevelopmentMilestones
Namespace Prefix:	nktr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Potential Reduction In Future Royalty Payments To Repay Post Approval Studies

+ References

No definition available.

+ Details

Name:	nktr_PotentialReductionInFutureRoyaltyPaymentsToRepayPostApprovalStudies
Namespace Prefix:	nktr_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Potential royalty reduction on US sales to repay post-approval study if required

+ References

No definition available.

+ Details

Name:	nktr_PotentialRoyaltyReductionOnUsSalesToRepayPostApprovalStudyIfRequired
Namespace Prefix:	nktr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Upfront and Milestone Payments Received Under License Agreement

+ References

No definition available.

+ Details

Name:	nktr_UpfrontAndMilestonePaymentsReceivedUnderLicenseAgreement
Namespace Prefix:	nktr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 13

-Section A

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 605

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 13.A.4(a).Q1 Response)

-URI http://asc.fasb.org/extlink&oid=27012821&loc=d3e214044-122780

+ Details

Name:	us-gaap_DeferredRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DeferredRevenueArrangementLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of consideration recognized during the period for the milestone or milestones.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 605

-SubTopic 28

-Section 50

-Paragraph 2

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=19771982&loc=SL6892177-166501

+ Details

Name:	us-gaap_RevenueRecognitionMilestoneMethodRevenueRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=nktr_AmgenIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=nktr_AstraZenecaAbMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=nktr_BaxterHealthcareMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=nktr_BayerHealthcareLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=nktr_OphthotechCorporationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=nktr_OtherPartnerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=nktr_RocheMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

License and Collaboration Agreements - Additional Information (Detail) (USD $)	3 Months Ended	1 Months Ended		3 Months Ended	1 Months Ended	0 Months Ended		1 Months Ended	3 Months Ended	1 Months Ended	12 Months Ended	1 Months Ended
	Mar. 31, 2015	Dec. 31, 2013	Feb. 29, 2012	Dec. 31, 2010	Jun. 30, 2014	Mar. 31, 2015	Sep. 16, 2014	Oct. 31, 2014	Dec. 31, 2009	Jun. 30, 2013	Dec. 31, 2007	Sep. 30, 2014	Jul. 31, 2016	Jul. 31, 2015
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones	$ 128,300,000nktr_PotentialDevelopmentMilestones
Roche [Member] \| MIRCERA [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue	9,400,000					9,400,000
Consideration received for product delivered in 2013		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 [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue	3,800,000					3,800,000
Roche [Member] \| PEGASYS and MIRCERA [Member]
Deferred Revenue Arrangement [Line Items]
Deferred revenue	4,000,000					4,000,000
Amgen, Inc. [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments				50,000,000
Deferred revenue	27,900,000					27,900,000
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					19,750,000
Deferred revenue	18,600,000					18,600,000
AstraZeneca AB [Member] \| United States [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments						100,000,000
Liability to AZ for DTC advertising payments	10,000,000					10,000,000
Reduction of revenue	(10,000,000)
AstraZeneca AB [Member] \| United States [Member] \| Other Current Liabilities [Member]
Deferred Revenue Arrangement [Line Items]
Liability to AZ for DTC advertising payments	5,000,000					5,000,000
AstraZeneca AB [Member] \| United States [Member] \| Other Long-Term Liabilities [Member]
Deferred Revenue Arrangement [Line Items]
Liability to AZ for DTC advertising payments	5,000,000					5,000,000
AstraZeneca AB [Member] \| Scenario, Forecast [Member] \| United States [Member]
Deferred Revenue Arrangement [Line Items]
Liability to AZ for DTC advertising payments													5,000,000	5,000,000
AstraZeneca AB [Member] \| MOVANTIK [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments	100,000,000						70,000,000	35,000,000
Potential reduction in U.S. royalty rate for repayment							2.00%
Percentage of post approval study costs to repay							33.00%
Maximum potential reduction in royalties							35,000,000
AstraZeneca AB [Member] \| MOVANTIK [Member] \| European Union [Member]
Deferred Revenue Arrangement [Line Items]
Contingent payments receivable based on development events regulatory to be pursued and completed solely by others	40,000,000					40,000,000
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					75,000,000
Bayer Healthcare LLC [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones	50,000,000
Deferred revenue	20,400,000					20,400,000
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
Bayer Healthcare LLC [Member] \| Upfront Payment Arrangement in 2007 [Member]
Deferred Revenue Arrangement [Line Items]
Received upfront and milestone payments											40,000,000
Baxter Healthcare [Member] \| BAX 855 (Hemophilia) [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones	20,000,000
Deferred revenue	0					0
Development milestones achieved												8,000,000
Baxter Healthcare [Member] \| BAX 855 (Hemophilia) [Member] \| United States [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones	10,000,000
Other [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones	$ 51,800,000