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

Estimated Annual Interest Rate

+ References

No definition available.

+ Details

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

- Definition

Payment To Bayer For Reimbursement Of Costs

+ References

No definition available.

+ Details

Name:	nktr_PaymentToBayerForReimbursementOfCosts
Namespace Prefix:	nktr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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 milestone repayments, principal amounts

+ References

No definition available.

+ Details

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

- Definition

Potential Reduced Royalty Rate Used To Repay Milestone

+ References

No definition available.

+ Details

Name:	nktr_PotentialReducedRoyaltyRateUsedToRepayMilestone
Namespace Prefix:	nktr_
Data Type:	num:percentItemType
Balance Type:	na
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_
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License and Collaboration Agreements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	0 Months Ended		3 Months Ended	1 Months Ended	2 Months Ended			0 Months Ended						0 Months Ended				1 Months Ended	3 Months Ended		12 Months Ended		3 Months Ended
	Mar. 31, 2014	Sep. 25, 2013 Naloxegol [Member]	Mar. 31, 2014 Naloxegol [Member] US and EU Commercial Launch [Member]	Mar. 31, 2014 Roche [Member] MIRCERA [Member]	Feb. 29, 2012 Roche [Member] MIRCERA [Member] Performance-based Milestone Payments [Member]	Feb. 29, 2012 Roche [Member] MIRCERA [Member] Upfront Payment Arrangement in 2007 [Member]	Mar. 31, 2014 Roche [Member] PEGASYS [Member]	Mar. 31, 2014 Roche [Member] PEGASYS and MIRCERA [Member]	Sep. 16, 2013 AstraZeneca AB [Member]	Sep. 16, 2013 AstraZeneca AB [Member] January 15, 2015 [Member]	Sep. 16, 2013 AstraZeneca AB [Member] Second Installment [Member]	Sep. 16, 2013 AstraZeneca AB [Member] January 15, 2017 [Member]	Sep. 16, 2013 AstraZeneca AB [Member] January 15, 2018 [Member]	Mar. 31, 2014 AstraZeneca AB [Member] FDA Acceptance [Member]	Sep. 16, 2013 AstraZeneca AB [Member] Naloxegol [Member]	Mar. 31, 2014 AstraZeneca AB [Member] Naloxegol [Member]	Mar. 31, 2014 AstraZeneca AB [Member] Naloxegol [Member] Pre-approval Cardiovascular Safety Study Not Required [Member]	Mar. 31, 2014 AstraZeneca AB [Member] Naloxegol Fixed-dose Combination Program [Member]	Jun. 30, 2013 Bayer Healthcare LLC [Member]	Mar. 31, 2014 Bayer Healthcare LLC [Member]	Mar. 31, 2014 Bayer Healthcare LLC [Member] Performance-based Milestone Payments [Member]	Dec. 31, 2007 Bayer Healthcare LLC [Member] Upfront Payment Arrangement in 2007 [Member]	Mar. 31, 2014 Amgen, Inc. [Member]	Mar. 31, 2014 Baxter Healthcare [Member] BAX 855 (Hemophilia) [Member]	Mar. 31, 2014 Other Member [Member]
Deferred Revenue Arrangement [Line Items]
Potential future additional payments for development milestones	$ 144.3																			$ 50.0				$ 28.0	$ 66.3
Contingent payments receivable based on development events regulatory to be pursued and completed solely by others			140.0											70.0		175.0	35.0	75.0
Development milestones achieved		25.0
Contingent repayments of payment received									70.0	10.0	10.0	20.0	30.0
Accrued interest rate									4.50%
Reduction on non-U.S. royalty for repayment															50.00%
Potential reduction in US royalty rate for repayment															2.00%
Maximum potential reduction in royalties															35.0
Deferred revenue				14.8			9.0	6.3												22.1			32.9	0
Received upfront and milestone payments					22.0	5.0															30.0	40.0
Consideration received for product delivered in 2013				18.6
Performance milestone payment to Bayer																			$ 10.0