v3.19.3.a.u2

UNIT-BASED COMPENSATION Narrative 3 (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
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 | $ 9.3 | $ 6.2 | $ 6.5
Units issued to satisfy award vestings, net of tax (units) | 242,199 | 189,399 | 152,017
Unrecognized compensation cost | $ 32.5 |  |
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 | $ 2.1 |  | $ 2.9
Units issued to satisfy award vestings, net of tax (units) | 50,054 |  | 33,438
Unit-based compensation, description of performance units | Performance units are issued to certain of our key employees and represent rights to receive our common units upon achieving performance measures for the performance period established by the NuStar GP, LLC Compensation Committee for the following year. Achievement of the performance measures determines the rate at which the performance units convert into our common units, which ranges from zero to 200% for certain awards. |  |
Unit-based compensation, terms of performance units | Performance units awarded vest in three annual increments (tranches), based upon our achievement of the performance measures set by the Compensation Committee during the one-year performance periods that end on December 31 of each applicable year. |  |
Unit-based compensation, requisite service period | 1 year |  |

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