v3.8.0.1

FAIR VALUE MEASUREMENTS (Tables) | 12 Months Ended
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Dec. 31, 2017
Fair Value Disclosures [Abstract] |
Fair Value, Measurement Inputs, Disclosure [Text Block] | The following assets and liabilities are measured at fair value on a recurring basis:
| December 31, 2017
| Level 1 |  | Level 2 |  | Level 3 |  | Total
| (Thousands of Dollars)
Assets: |  |  |  |  |  |  |
Other current assets: |  |  |  |  |  |  |
Product imbalances | $ | 3,890 |  |  | $ | — |  |  | $ | — |  |  | $ | 3,890 |
Liabilities: |  |  |  |  |  |  |
Accrued liabilities: |  |  |  |  |  |  |
Product imbalances | $ | (1,534 | ) |  | $ | — |  |  | $ | — |  |  | $ | (1,534 | )
Commodity derivatives | (878 | ) |  | — |  |  | — |  |  | (878 | )
Interest rate swaps | — |  |  | (5,394 | ) |  | — |  |  | (5,394 | )
Other long-term liabilities: |  |  |  |  |  |  |
Interest rate swaps | — |  |  | (4,594 | ) |  | — |  |  | (4,594 | )
Total | $ | (2,412 | ) |  | $ | (9,988 | ) |  | $ | — |  |  | $ | (12,400 | )
| December 31, 2016
| Level 1 |  | Level 2 |  | Level 3 |  | Total
| (Thousands of Dollars)
Assets: |  |  |  |  |  |  |
Other current assets: |  |  |  |  |  |  |
Product imbalances | $ | 1,551 |  |  | $ | — |  |  | $ | — |  |  | $ | 1,551 |
Commodity derivatives | — |  |  | 155 |  |  | — |  |  | 155 |
Other long-term assets, net: |  |  |  |  |  |  |
Interest rate swaps | — |  |  | 1,314 |  |  | — |  |  | 1,314 |
Total | $ | 1,551 |  |  | $ | 1,469 |  |  | $ | — |  |  | $ | 3,020 |
Liabilities: |  |  |  |  |  |  |
Accrued liabilities: |  |  |  |  |  |  |
Product imbalances | $ | (1,577 | ) |  | $ | — |  |  | $ | — |  |  | $ | (1,577 | )
Commodity derivatives | (4,887 | ) |  | (165 | ) |  | — |  |  | (5,052 | )
Other long-term liabilities: |  |  |  |  |  |  |
Guarantee liability | — |  |  | — |  |  | (1,230 | ) |  | (1,230 | )
Interest rate swaps | — |  |  | (2,632 | ) |  | — |  |  | (2,632 | )
Total | $ | (6,464 | ) |  | $ | (2,797 | ) |  | $ | (1,230 | ) |  | $ | (10,491 | )
Fair Value and Carrying Value of Debt and Note Receivable [Text Block] | The estimated fair values and carrying amounts of the long-term debt, including the current portion, and the Axeon Term Loan were as follows:
| December 31, 2017 |  | December 31, 2016
| Long-term Debt |  | Long-term Debt |  | Axeon Term Loan
| (Thousands of Dollars)
Fair value | $ | 3,677,622 |  |  | $ | 3,084,762 |  |  | $ | 110,000 |
Carrying amount | $ | 3,613,059 |  |  | $ | 3,014,364 |  |  | $ | 110,000 |

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- Definition Fair Value and Carrying Value of Debt and Note Receivable [Table Text Block] + References No definition available. + Details
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- References No definition available. + Details
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- Definition The entire disclosure of the fair value measurement of assets and liabilities, which includes financial instruments measured at fair value that are classified in shareholders' equity, which may be measured on a recurring or nonrecurring basis. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -URI http://asc.fasb.org/topic&trid=2155941 + Details
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