| Fair Value Measurements, Recurring and Nonrecurring [Table Text Block] |
The following assets and liabilities are measured at fair value on a recurring basis: | | | | | | | | | | | | | | | | | | September 30, 2014 | | Level 1 | | Level 2 | | Level 3 | | Total | | (Thousands of Dollars) | Assets: | | | | | | | | Other current assets: | | | | | | | | Product imbalances | $ | 2,822 |
| | $ | — |
| | $ | — |
| | $ | 2,822 |
| Commodity derivatives | 6,714 |
| | 3,166 |
| | — |
| | 9,880 |
| Other long-term assets, net: | | | | | | | | Commodity derivatives | — |
| | 233 |
| | — |
| | 233 |
| Total | $ | 9,536 |
| | $ | 3,399 |
| | $ | — |
| | $ | 12,935 |
| Liabilities: | | | | | | | | Accrued liabilities: | | | | | | | | Product imbalances | $ | (2,335 | ) | | $ | — |
| | $ | — |
| | $ | (2,335 | ) | Commodity derivatives | — |
| | (1,615 | ) | | — |
| | (1,615 | ) | Other long-term liabilities: | | | | | | | | Commodity derivatives | — |
| | (105 | ) | | — |
| | (105 | ) | Guarantee liability | — |
| | — |
| | (1,730 | ) | | (1,730 | ) | Total | $ | (2,335 | ) | | $ | (1,720 | ) | | $ | (1,730 | ) | | $ | (5,785 | ) |
| | | | | | | | | | | | | | | | | | December 31, 2013 | | Level 1 | | Level 2 | | Level 3 | | Total | | (Thousands of Dollars) | Assets: | | | | | | | | Other current assets: | | | | | | | | Product imbalances | $ | 1,980 |
| | $ | — |
| | $ | — |
| | $ | 1,980 |
| Commodity derivatives | — |
| | 4,948 |
| | — |
| | 4,948 |
| Other long-term assets, net: | | | | | | | | Commodity derivatives | — |
| | 6,977 |
| | — |
| | 6,977 |
| Total | $ | 1,980 |
| | $ | 11,925 |
| | $ | — |
| | $ | 13,905 |
| Liabilities: | | | | | | | | Accrued liabilities: | | | | | | | | Product imbalances | $ | (2,190 | ) | | $ | — |
| | $ | — |
| | $ | (2,190 | ) | Commodity derivatives | (1,433 | ) | | (800 | ) | | — |
| | (2,233 | ) | Contingent consideration | — |
| | — |
| | (1,318 | ) | | (1,318 | ) | Other long-term liabilities: | | | | | | | | Commodity derivatives | — |
| | (1,575 | ) | | — |
| | (1,575 | ) | Guarantee liability | — |
| | — |
| | (1,880 | ) | | (1,880 | ) | Total | $ | (3,623 | ) | | $ | (2,375 | ) | | $ | (3,198 | ) | | $ | (9,196 | ) |
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| Fair Value and Carrying Value of Debt and Note Receivable [Table Text Block] |
The estimated fair value and carrying amounts of the debt and note receivable were as follows: | | | | | | | | | | | | | | | | | | September 30, 2014 | | December 31, 2013 | | Fair Value | | Carrying Amount | | Fair Value | | Carrying Amount | | (Thousands of Dollars) | Long-term debt | $ | 2,783,666 |
| | $ | 2,731,551 |
| | $ | 2,636,734 |
| | $ | 2,655,553 |
| Note receivable from Axeon | $ | 148,300 |
| | $ | 170,385 |
| | $ | 133,416 |
| | $ | 165,440 |
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