| Document and Entity Information | Sep. 09, 2020 |
| Entity Listings [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Sep. 9, 2020 |
| Entity Registrant Name | NuStar Energy L.P. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-16417 |
| Entity Tax Identification Number | 74-2956831 |
| Entity Address, Address Line One | 19003 IH-10 West |
| Entity Address, City or Town | San Antonio |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 78257 |
| City Area Code | 210 |
| Local Phone Number | 918-2000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001110805 |
| Common Stock [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Common units |
| Trading Symbol | NS |
| Security Exchange Name | NYSE |
| Series A Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Units [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Series A Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Units |
| Trading Symbol | NSprA |
| Security Exchange Name | NYSE |
| Series B Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Units [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Series B Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Units |
| Trading Symbol | NSprB |
| Security Exchange Name | NYSE |
| Series C Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Units [Member] | |
| Entity Listings [Line Items] | |
| Title of 12(b) Security | Series C Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Units |
| Trading Symbol | NSprC |
| Security Exchange Name | NYSE |
