v3.19.3.a.u2

REVENUE FROM CONTRACTS WITH CUSTOMERS Narrative (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended | 12 Months Ended | 15 Months Ended
--- | --- | --- | --- | ---
Jun. 30, 2018 | Sep. 30, 2018 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2019
Revenue recognized |  |  | $ 77,466 | $ 57,826 |
Additions to contract liability |  |  | $ 52,957 | $ 83,243 |
Revenue recognized due to change in contract liability | $ 9,000 |  |  |  |
Unnamed Customer [Member] |  |  |  |  |
Revenue recognized |  |  |  |  | $ 37,500
Additions to contract liability |  | $ 37,500 |  |  |

X
- Definition Contract with Customer, Liability, Additions + References No definition available. + Details
Name: | ns_ContractwithCustomerLiabilityAdditions
Namespace Prefix: | ns_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of revenue recognized arising from contract liability from change in timeframe for performance obligation to be satisfied. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130551-203045 + Details
Name: | us-gaap_ContractWithCustomerLiabilityChangeInTimeframePerformanceObligationSatisfiedRevenueRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130549-203045 + Details
Name: | us-gaap_ContractWithCustomerLiabilityRevenueRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | srt_MajorCustomersAxis=ns_UnnamedCustomerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |