UNIT-BASED COMPENSATION Narrative 3 (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Restricted Units [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Total fair value of restricted units that vested during the period | $ 4,600 | $ 9,300 | $ 6,200 |
| Units issued to satisfy award vestings, net of tax (units) | 275,146 | 242,199 | 189,399 |
| Unrecognized compensation cost | $ 38,100 | ||
| Compensation cost not yet recognized, period for recognition | 3 years 9 months 18 days | ||
| Performance Units [Member] | |||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Total fair value of restricted units that vested during the period | $ 4,200 | $ 2,100 | |
| Units issued to satisfy award vestings, net of tax (units) | 93,440 | 50,054 | |
| Unit-based compensation, description of performance units | Performance awards are issued to certain of our key employees and represent either rights to receive our common units or cash upon achieving performance measures for the performance period established by the NuStar GP, LLC Compensation Committee. Achievement of the performance measures determines the rate at which the performance awards convert into our common units or cash, which ranges from zero to 200% for certain awards. | ||
| Unit-based compensation, terms of performance units | Performance awards vest in three annual increments (tranches), based upon our achievement of the performance measures set by the Compensation Committee during the performance periods that end on December 31 of each applicable year. | ||
| Unit-based compensation, requisite service period | 1 year | ||