| Fair Value Measurements, Recurring and Nonrecurring [Table Text Block] |
The following assets and liabilities are measured at fair value on a recurring basis: | | | | | | | | | | | | | | | | | | March 31, 2014 | | Level 1 | | Level 2 | | Level 3 | | Total | | (Thousands of Dollars) | Other current assets: | | | | | | | | Product imbalances | $ | 2,470 |
| | $ | — |
| | $ | — |
| | $ | 2,470 |
| Commodity derivatives | 579 |
| | 4,695 |
| | — |
| | 5,274 |
| Other long-term assets, net: | | | | | | | | Commodity derivatives | — |
| | 794 |
| | — |
| | 794 |
| Accrued liabilities: | | | | | | | | Product imbalances | (2,157 | ) | | — |
| | — |
| | (2,157 | ) | Commodity derivatives | — |
| | (2,574 | ) | | — |
| | (2,574 | ) | Contingent consideration | — |
| | — |
| | (1,318 | ) | | (1,318 | ) | Other long-term liabilities: | | | | | | | | Commodity derivatives | — |
| | (411 | ) | | — |
| | (411 | ) | Guarantee liability | — |
| | — |
| | (2,620 | ) | | (2,620 | ) | Total | $ | 892 |
| | $ | 2,504 |
| | $ | (3,938 | ) | | $ | (542 | ) |
| | | | | | | | | | | | | | | | | | December 31, 2013 | | Level 1 | | Level 2 | | Level 3 | | Total | | (Thousands of Dollars) | 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 |
| 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 | $ | (1,643 | ) | | $ | 9,550 |
| | $ | (3,198 | ) | | $ | 4,709 |
|
|
| 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: | | | | | | | | | | | | | | | | | | March 31, 2014 | | December 31, 2013 | | Fair Value | | Carrying Amount | | Fair Value | | Carrying Amount | | (Thousands of Dollars) | Debt | $ | 2,764,360 |
| | $ | 2,710,117 |
| | $ | 2,636,734 |
| | $ | 2,655,553 |
| Note receivable from Asphalt JV | $ | 144,949 |
| | $ | 171,275 |
| | $ | 133,416 |
| | $ | 165,440 |
|
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