v3.21.2

DERIVATIVES Narrative 1 (Details) - USD ($) $ in Thousands | 1 Months Ended | 5 Months Ended | 9 Months Ended
--- | --- | --- | ---
Jun. 30, 2020 | May 31, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Payments for termination of interest rate swaps | $ (49,200) |  | $ 0 | $ 49,225
Interest rate swaps | Cash Flow Hedges |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Interest rate swaps, interest rate received |  | received a rate based on the three-month USD LIBOR. |  |
Notional amount of forward-starting interest rate swaps terminated |  | $ 250,000 |  |

X
- Definition Aggregate notional amount that was terminated, specified by the derivative(s). + References No definition available. + Details
Name: | ns_DerivativeNotionalAmountTerminated
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 Proceeds from (payments for) termination of interest rate swap agreements + References No definition available. + Details
Name: | ns_ProceedsFromPaymentsForTerminationOfInterestRateSwaps
Namespace Prefix: | ns_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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_DerivativeInstrumentsGainLossLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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: |