v3.19.3.a.u2

LEASE ASSETS AND LIABILITIES Narrative 2 (Details) | 12 Months Ended
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Dec. 31, 2019
Operating Lease Type [Line Items] |
Lessee, operating lease, renewal term | 20 years
Lessee, Finance Lease, Description [Abstract] |
Lessee, finance lease, remaining term | 1 year
Number of renewal periods | 4
Lessee, finance lease, renewal term | 5 years
Maximum [Member] |
Operating Lease Type [Line Items] |
Lessee, operating lease, remaining term | 6 years

X
- Definition Remaining term of lessee's finance lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | ns_Lesseefinanceleaseremainingterm
Namespace Prefix: | ns_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Remaining term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | ns_Lesseeoperatingleaseremainingterm
Namespace Prefix: | ns_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of renewal periods on finance leases + References No definition available. + Details
Name: | ns_Numberofrenewalperiods
Namespace Prefix: | ns_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition [Line Items] for Operating Lease Type [Table] + References No definition available. + Details
Name: | ns_OperatingLeaseTypeLineItems
Namespace Prefix: | ns_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_LesseeFinanceLeaseDescriptionAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Term of lessee's finance lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980 + Details
Name: | us-gaap_LesseeFinanceLeaseRenewalTerm1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Definition Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980 + Details
Name: | us-gaap_LesseeOperatingLeaseRenewalTerm
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |