SEGMENT INFORMATION Narrative (Details) - USD ($) $ in Thousands |
3 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 31, 2017 |
Sep. 30, 2017 |
Jun. 30, 2017 |
Mar. 31, 2017 |
Dec. 31, 2016 |
Sep. 30, 2016 |
Jun. 30, 2016 |
Mar. 31, 2016 |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Revenue, Major Customer [Line Items] | |||||||||||
| Revenue from largest customer | $ 450,535 | $ 440,566 | $ 435,488 | $ 487,430 | $ 471,757 | $ 441,418 | $ 437,804 | $ 405,703 | $ 1,814,019 | $ 1,756,682 | $ 2,084,040 |
| Sales Revenue, Net [Member] | Valero Energy Corporation [Member] | |||||||||||
| Revenue, Major Customer [Line Items] | |||||||||||
| Largest customer percentage of revenue | 17.00% | 18.00% | 16.00% | ||||||||
| Revenue from largest customer | $ 300,000 | $ 310,000 | $ 331,700 | ||||||||