MERGER AND RELATED PARTY AGREEMENTS Narrative 1 (Details) - USD ($) $ in Millions |
6 Months Ended | 9 Months Ended | 12 Months Ended | |||
|---|---|---|---|---|---|---|
Jun. 30, 2018 |
Sep. 30, 2018 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Jul. 20, 2018 |
|
| Class of Stock [Line Items] | ||||||
| General partner ownership interest | 2.00% | 2.00% | ||||
| Common unit conversion rate | 55.00% | |||||
| Approximate cash consideration for merger | $ 68.0 | |||||
| Number of common limited partner units owned by general partner | 10,200,000 | |||||
| Common Limited Partner [Member] | ||||||
| Class of Stock [Line Items] | ||||||
| Issuance of NuStar Energy common units as a result of the Merger, units issued | 23,600,000 | |||||
| Issuance of NuStar Energy common units as a result of the Merger, incremental units issued | 13,400,000 | 0 | 13,409,593 | 0 | ||