| Fair Value, Measurement Inputs, Disclosure [Text Block] |
The following assets and liabilities are measured at fair value: | | | | | | | | | | | | | | | | | | September 30, 2012 | | Level 1 | | Level 2 | | Level 3 | | Total | | (Thousands of Dollars) | Other current assets: | | | | | | | | Product imbalances | $ | 898 |
| | $ | — |
| | $ | — |
| | $ | 898 |
| Commodity derivatives | 19,013 |
| | 2,365 |
| | — |
| | 21,378 |
| Other long-term assets, net: | | | | | | | | Commodity derivatives | — |
| | 6,675 |
| | — |
| | 6,675 |
| Accrued liabilities: | | | | | | | | Product imbalances | (577 | ) | | — |
| | — |
| | (577 | ) | Commodity derivatives | (5,929 | ) | | (20,861 | ) | | — |
| | (26,790 | ) | Interest rate swaps | — |
| | (41,117 | ) | | — |
| | (41,117 | ) | Other long-term liabilities: | | | | | | | | Commodity derivatives | — |
| | (1,265 | ) | | — |
| | (1,265 | ) | Total | $ | 13,405 |
| | $ | (54,203 | ) | | $ | — |
| | $ | (40,798 | ) |
| | | | | | | | | | | | | | | | | | December 31, 2011 | | Level 1 | | Level 2 | | Level 3 | | Total | | (Thousands of Dollars) | Other current assets: | | | | | | | | Product imbalances | $ | 2,117 |
| | $ | — |
| | $ | — |
| | $ | 2,117 |
| Commodity derivatives | 10,282 |
| | 1,830 |
| | — |
| | 12,112 |
| Other long-term assets, net: | | | | | | | | Commodity derivatives | — |
| | 27,084 |
| | — |
| | 27,084 |
| Interest rate swaps | — |
| | 2,335 |
| | — |
| | 2,335 |
| Accrued liabilities: | | | | | | | | Product imbalances | (1,469 | ) | | — |
| | — |
| | (1,469 | ) | Commodity derivatives | (5,424 | ) | | — |
| | — |
| | (5,424 | ) | Interest rate swaps | — |
| | (22,009 | ) | | — |
| | (22,009 | ) | Other long-term liabilities: | | | | | | | | Interest rate swaps | — |
| | (27,190 | ) | | — |
| | (27,190 | ) | Total | $ | 5,506 |
| | $ | (17,950 | ) | | $ | — |
| | $ | (12,444 | ) |
|
| Fair Value and Carrying Value of Debt [Text Block] |
The estimated fair value and carrying amount of our debt was as follows: | | | | | | | | | | September 30,
2012 | | December 31,
2011 | | (Thousands of Dollars) | Fair value | $ | 2,018,993 |
| | $ | 2,377,565 |
| Carrying amount | $ | 2,036,406 |
| | $ | 2,293,030 |
|
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