v3.8.0.1

DERIVATIVES AND RISK MANAGEMENT ACTIVITIES Narrative (Details) bbl in Millions |  |  | 12 Months Ended
--- | --- | --- | ---
Dec. 31, 2017 USD ($) bbl | Dec. 31, 2016 USD ($) bbl | Dec. 31, 2017 USD ($)
Interest rate swaps |  |  |
Derivative [Line Items] |  |  |
Fair market value of unwound fixed-to-floating interest rate swap | $ 15,600,000 | $ 21,100,000 | $ 15,600,000
Fair market value of unwound forward starting interest rate swap | 14,300,000 | 20,900,000 | $ 14,300,000
Interest rate swaps | Cash Flow Hedges |  |  |
Derivative [Line Items] |  |  |
Interest rate swaps interest rate received |  |  | receive a rate based on the three-month USD LIBOR
Notional amount of interest rate swaps | $ 600,000,000.0 | $ 600,000,000.0 | $ 600,000,000.0
Commodity contracts |  |  |
Derivative [Line Items] |  |  |
Notional amount of commodity contracts, in barrels | bbl | 1.2 | 4.7 |
Margin deposit assets | $ 300,000 | $ 1,800,000 | $ 300,000

X
- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
Name: | invest_DerivativeNotionalAmount
Namespace Prefix: | invest_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Definition Fair value amount of unwound fixed-to-floating interest rate swap included in the balance sheet. + References No definition available. + Details
Name: | ns_FairMarketValueofUnwoundFixedtoFloatingInterestRateSwaps
Namespace Prefix: | ns_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair value amount of unwound forward starting interest rate swap included in the balance sheet. + References No definition available. + Details
Name: | ns_FairMarketValueofUnwoundForwardStartingInterestRateSwaps
Namespace Prefix: | ns_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Interest rate received under the terms of the interest rate swap agreements. + References No definition available. + Details
Name: | ns_InterestRateSwapsInterestRateReceived
Namespace Prefix: | ns_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- 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_DerivativeLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Nominal volume used to calculate payments on a derivative instrument. + References No definition available. + Details
Name: | us-gaap_DerivativeNonmonetaryNotionalAmountVolume
Namespace Prefix: | us-gaap_
Data Type: | num:volumeItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of cash or securities placed with a broker or counterparty as security for a trading or derivatives securities position which was partially obtained with funds provided by the broker dealer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.8,17) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_MarginDepositAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_CashFlowHedgingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CommodityContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |