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Leases - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | 12 Months Ended |
--- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Sep. 30, 2009 sqft
Leases [Line Items] |  |  |  |
Percentage ceiling on rent increases, annually, capital lease | 3.00%nktr_PercentageCeilingOnRentIncrease |  |  |
San Carlos facility capital leases, termination date | Oct. 05, 2016 |  |  |
Future minimum rental receipts under the San Carlos facility subleases | $ 4.8 us-gaap_CapitalLeasesFutureMinimumSubleaseRentals |  |  |
Book value of assets, gross | 2.7 us-gaap_CapitalLeasedAssetsGross | 2.3 us-gaap_CapitalLeasedAssetsGross |  |
Net book value of assets | 1.2 us-gaap_CapitalLeasesBalanceSheetAssetsByMajorClassNet | 1.0 us-gaap_CapitalLeasesBalanceSheetAssetsByMajorClassNet |  |
Operating Sublease term commenced start date | August 2010 |  |  |
Operating Sublease term commenced period | 114 months |  |  |
Operating Sublease term commenced end date | January 31, 2020 |  |  |
Rent expense for operating leases | $ 3.2 us-gaap_LeaseAndRentalExpense | $ 2.9 us-gaap_LeaseAndRentalExpense | $ 2.8 us-gaap_LeaseAndRentalExpense |
Pfizer, Inc. [Member] |  |  |  |
Leases [Line Items] |  |  |  |
Operating sublease |  |  |  | 126,285 nktr_OperatingSublease / dei_LegalEntityAxis = nktr_PfizerMember

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- Definition Capital leases termination date. + References No definition available. + Details
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Namespace Prefix: | nktr_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | nktr_LeasesLineItems
Namespace Prefix: | nktr_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Operating sublease. + References No definition available. + Details
Name: | nktr_OperatingSublease
Namespace Prefix: | nktr_
Data Type: | num:areaItemType
Balance Type: | na
Period Type: | instant

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- Definition Percentage ceiling on rent increase. + References No definition available. + Details
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- Definition Sublease term commenced end date. + References No definition available. + Details
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- Definition Sublease term commenced Period. + References No definition available. + Details
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Balance Type: | na
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- Definition Sublease term commenced start date. + References No definition available. + Details
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Data Type: | us-types:dateStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount before accumulated depreciation of leased physical assets used in the normal conduct of business to produce goods and services. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6455314&loc=d3e45014-112735 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition The total gross amount less the charge for the use of the long-lived depreciable assets subject to a lease meeting the criteria for capitalization. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6455398&loc=d3e45280-112737 + Details
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- Definition Minimum payments receivable in the future under noncancelable subleases. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6455398&loc=d3e45280-112737 + Details
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- Definition Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line. + References No definition available. + Details
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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |