Aggregate consideration received from agreements.

No definition available.

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

- Definition

Amount of transaction price allocated to performance obligation.

+ References

No definition available.

+ Details

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

- Definition

Collaborative arrangements maximum aggregate additional cash payments receivable upon achievement of development and regulatory milestones.

+ References

No definition available.

+ Details

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

- Definition

Eligible additional cash payments receivable upon achievement of certain sales milestones.

+ References

No definition available.

+ Details

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

- Definition

Estimated fair value of shares.

+ References

No definition available.

+ Details

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

- Definition

Payments received under rights to sublicense agreement.

+ References

No definition available.

+ Details

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

- Definition

Percentage of development milestones payments, to be received, if conditions occur.

+ References

No definition available.

+ Details

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

- Definition

Percentage of development milestones payments, to be received under certain conditions.

+ References

No definition available.

+ Details

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

- Definition

Percentage of funding Phase three development costs on an indication by indication basis borne.

+ References

No definition available.

+ Details

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

- Definition

Percentage of sharing in development costs.

+ References

No definition available.

+ Details

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

- Definition

Percentage of sharing in Phase 2 development costs.

+ References

No definition available.

+ Details

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

- Definition

Percentage of sharing in production costs.

+ References

No definition available.

+ Details

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

- Definition

Percentage of upfront payment, market access milestone payments, royalties and sales milestone payments.

+ References

No definition available.

+ Details

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

- Definition

Percentage of upfront payment market access milestone payments royalties and sales milestone payments from sublicense agreement retained by our collaboration partner.

+ References

No definition available.

+ Details

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

- Definition

Potential development and regulatory milestones.

+ References

No definition available.

+ Details

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

- Definition

Potential development milestones.

+ References

No definition available.

+ Details

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

- Definition

Potential development regulatory and sales milestones.

+ References

No definition available.

+ Details

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

- Definition

Profits and losses sharing percentage.

+ References

No definition available.

+ Details

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

- Definition

Reimbursement of expenses.

+ References

No definition available.

+ Details

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

- Definition

Remaining amount allocated to transaction price.

+ References

No definition available.

+ Details

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

- Definition

Sale of stock consideration received.

+ References

No definition available.

+ Details

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

- Definition

Sales Milestone Revenue

+ References

No definition available.

+ Details

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

- Definition

Upfront and milestone payments received from license agreements.

+ References

No definition available.

+ Details

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

- Definition

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121566466&loc=d3e6676-107765

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4531-111522

+ Details

Name:	us-gaap_AccountsReceivableNetCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121556615&loc=SL49130531-203044

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130549-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121556615&loc=SL49130532-203044

+ Details

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

- Definition

Amount of revenue recognized from performance obligation satisfied or partially satisfied in previous reporting periods. Includes, but is not limited to, change in transaction price.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12A
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL108322424-203045

+ Details

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

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9031-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9038-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130543-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9054-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130545-203045

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

+ Details

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

- Definition

Number of shares of stock issued as of the balance sheet date, including shares that had been issued and were previously outstanding but which are now held in the treasury.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

+ Details

Name:	us-gaap_SharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_TypeOfArrangementAxis=nktr_BMSCollaborationAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=nktr_NektarTwoOneFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=srt_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	nktr_MilestoneAxis=nktr_MilestoneOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	nktr_MilestoneAxis=nktr_MilestoneTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	nktr_MilestoneAxis=nktr_MilestoneThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis=nktr_OpdivoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis=nktr_OpdivoAndYervoyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=nktr_NektarThreeFiveEightMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=nktr_NektarMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=nktr_SharePurchaseAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_ResearchAndDevelopmentExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	srt_ProductOrServiceAxis=nktr_NektarThreeFiveEightMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201409Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=nktr_NektarThreeFiveEightLicenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=nktr_PhaseOneClinicalDevelopmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=nktr_DrugProductDevelopmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_TypeOfArrangementAxis=nktr_HemophiliaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ContractWithCustomerSalesChannelAxis=nktr_AnnualSalesLevelMilestoneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=us-gaap_EuropeanUnionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- 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:	us-gaap_TypeOfArrangementAxis=nktr_MOVANTIKAndMOVENTIGMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=nktr_AstraZenecaAgreementWithKirinMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

License and Collaboration Agreements - Additional Information (Detail) - USD ($)			1 Months Ended							3 Months Ended				6 Months Ended		12 Months Ended	76 Months Ended
	Feb. 13, 2018	Aug. 23, 2017	Mar. 31, 2020	Apr. 30, 2018	Jan. 31, 2018	Nov. 30, 2017	Sep. 30, 2017	Aug. 31, 2017	Mar. 31, 2016	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Dec. 31, 2010	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2015	Jan. 09, 2020	Dec. 31, 2019
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized in period related to performance in prior periods										$ 42,100,000				$ 86,700,000
Potential future additional development and regulatory milestones										1,700,000,000				1,700,000,000
Accounts receivable										47,245,000				47,245,000					$ 36,802,000
Revenue, excluding assessed tax										48,847,000		$ 23,315,000		99,420,000	$ 51,537,000
Deferred revenue										4,281,000				4,281,000					$ 8,071,000
BMS Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Sales milestone, revenue			$ 25,000,000.0							25,000,000.0				50,000,000.0
BMS Collaboration Agreement \| Bempegaldesleukin \| Nektar's
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Global commercialization profits and losses sharing percentage	65.00%
Percentage of sharing production costs	65.00%
Upfront and milestone payments received from license agreements				$ 1,000,000,000.0
Maximum total additional cash payments receivable upon achievement of certain development and regulatory milestones														1,455,000,000
BMS Collaboration Agreement \| Bempegaldesleukin \| Nektar's \| Milestone One
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones																		$ 25,000,000.0
BMS Collaboration Agreement \| Bempegaldesleukin \| Nektar's \| Milestone Two
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones																		25,000,000.0
BMS Collaboration Agreement \| Bempegaldesleukin \| Nektar's \| Milestone Three
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones																		$ 75,000,000.0
BMS Collaboration Agreement \| Bempegaldesleukin \| Nektar's \| Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible additional cash payments receivable upon achievement of certain sales milestones				$ 350,000,000.0
BMS Collaboration Agreement \| Bempegaldesleukin \| Nektar's \| Opdivo
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs	32.50%
BMS Collaboration Agreement \| Bempegaldesleukin \| Nektar's \| Opdivo and Yervoy
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs	22.00%
NKTR-358 \| Nektar's
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Received upfront and milestone payment							$ 150,000,000.0
Percentage of sharing in Phase 2 development costs		25.00%
Nektar
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of upfront payment, market access milestones, royalties and sales milestones									40.00%
Bristol-Myers Squibb Company \| Purchase Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Shares issued (in shares)				8,284,600
Sale of stock consideration received				$ 850,000,000.0
Bristol-Myers Squibb Company \| Bempegaldesleukin \| Research and Development Expense
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reimbursement of expenses										33,900,000		$ 24,600,000		65,100,000	$ 53,400,000
Bristol-Myers Squibb Company \| BMS Collaboration Agreement \| Purchase Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total consideration received under agreements																$ 1,850,000,000
Estimated fair value of shares																790,200,000
Remaining amount allocated to transaction price										25,000,000.0	$ 25,000,000.0			50,000,000.0		1,059,800,000
Potential future development, regulatory and sales milestones																1,800,000,000
Bristol-Myers Squibb Company \| BMS Collaboration Agreement \| Bempegaldesleukin
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Global commercialization profits and losses sharing percentage	35.00%
Percentage of sharing production costs	35.00%
Bristol-Myers Squibb Company \| BMS Collaboration Agreement \| Bempegaldesleukin \| Opdivo
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs	67.50%
Bristol-Myers Squibb Company \| BMS Collaboration Agreement \| Bempegaldesleukin \| Opdivo and Yervoy
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing development costs	78.00%
Eli Lilly and Company \| NKTR-358 \| ASC 606
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue, excluding assessed tax								$ 125,900,000
Eli Lilly and Company \| NKTR-358 License
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount of transaction price allocated to performance obligation							125,900,000
Eli Lilly and Company \| NKTR-358 \| Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional development and regulatory milestones		$ 250,000,000.0
Eli Lilly and Company \| NKTR-358 \| Nektar's
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of regulatory milestones payments will be reduced under certain conditions		50.00%
Percentage of regulatory milestones payments will be reduced if conditions occur		75.00%
Eli Lilly and Company \| NKTR-358 \| Nektar's \| Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of funding phase 3 development costs on an indication by indication basis borne		25.00%
Eli Lilly and Company \| NKTR-358 \| Nektar's \| Minimum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of funding phase 3 development costs on an indication by indication basis borne		0.00%
Eli Lilly and Company \| Phase 1 Clinical Development \| NKTR-358 License
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount of transaction price allocated to performance obligation							17,600,000
Eli Lilly and Company \| Drug Product Development \| NKTR-358 License
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount of transaction price allocated to performance obligation							$ 6,500,000
Eli Lilly \| NKTR-358
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of sharing in Phase 2 development costs		75.00%
Baxalta Incorporated/Takeda \| Hemophilia
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Received under right to sublicense agreement						$ 12,000,000.0
Baxalta Incorporated/Takeda \| Hemophilia \| Annual Sales Level Milestone
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue, excluding assessed tax																$ 10,000,000.0
Baxalta Incorporated/Takeda \| Hemophilia \| European Union
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue, excluding assessed tax					$ 10,000,000.0
Amgen, Inc.
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Received upfront and milestone payment													$ 50,000,000.0
Amgen, Inc. \| ASC 606
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue										1,700,000				1,700,000
AstraZeneca AB \| MOVANTIK and MOVENTIG
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Received upfront and milestone payment																	$ 385,000,000.0
AstraZeneca AB \| AstraZeneca-Kirin
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue										0				0
Percentage of upfront payment, market access milestone payments, royalties and sales milestone payments from sublicense agreement retained by our collaboration partner									60.00%
Other
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential future additional payments for development milestones										40,000,000.0				40,000,000.0
Deferred revenue										$ 2,000,000.0				$ 2,000,000.0