| 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, 2016 | | Level 1 | | Level 2 | | Level 3 | | Total | | (Thousands of Dollars) | Assets: | | | | | | | | Other current assets: | | | | | | | | Product imbalances | $ | 1,008 |
| | $ | — |
| | $ | — |
| | $ | 1,008 |
| Commodity derivatives | — |
| | 704 |
| | — |
| | 704 |
| Total | $ | 1,008 |
| | $ | 704 |
| | $ | — |
| | $ | 1,712 |
| Liabilities: | | | | | | | | Accrued liabilities: | | | | | | | | Product imbalances | $ | (1,344 | ) | | $ | — |
| | $ | — |
| | $ | (1,344 | ) | Commodity derivatives | (301 | ) | | (701 | ) | | — |
| | (1,002 | ) | Other long-term liabilities: | | | | | | | | Guarantee liability | — |
| | — |
| | (1,736 | ) | | (1,736 | ) | Interest rate swaps | — |
| | (50,910 | ) | | — |
| | (50,910 | ) | Total | $ | (1,645 | ) | | $ | (51,611 | ) | | $ | (1,736 | ) | | $ | (54,992 | ) |
| | | | | | | | | | | | | | | | | | December 31, 2015 | | Level 1 | | Level 2 | | Level 3 | | Total | | (Thousands of Dollars) | Assets: | | | | | | | | Other current assets: | | | | | | | | Product imbalances | $ | 179 |
| | $ | — |
| | $ | — |
| | $ | 179 |
| Commodity derivatives | 11,325 |
| | 77 |
| | — |
| | 11,402 |
| Other long-term assets, net: | | | | | | | | Interest rate swaps | — |
| | 2,755 |
| | — |
| | 2,755 |
| Total | $ | 11,504 |
| | $ | 2,832 |
| | $ | — |
| | $ | 14,336 |
| Liabilities: | | | | | | | | Accrued liabilities: | | | | | | | | Product imbalances | $ | (419 | ) | | $ | — |
| | $ | — |
| | $ | (419 | ) | Commodity derivatives | — |
| | (120 | ) | | — |
| | (120 | ) | Other long-term liabilities: | | | | | | | | Guarantee liability | — |
| | — |
| | (1,697 | ) | | (1,697 | ) | Interest rate swaps | — |
| | (1,452 | ) | | — |
| | (1,452 | ) | Total | $ | (419 | ) | | $ | (1,572 | ) | | $ | (1,697 | ) | | $ | (3,688 | ) |
|
| Fair Value and Carrying Value of Debt and Note Receivable [Table Text Block] |
The estimated fair values and carrying amounts of the long-term debt and the Axeon Term Loan were as follows: | | | | | | | | | | | | | | | | | | September 30, 2016 | | December 31, 2015 | | Fair Value | | Carrying Amount | | Fair Value | | Carrying Amount | | (Thousands of Dollars) | Long-term debt | $ | 3,214,845 |
| | $ | 3,153,049 |
| | $ | 2,929,438 |
| | $ | 3,055,612 |
| Axeon Term Loan | $ | 175,717 |
| | $ | 170,391 |
| | $ | 172,123 |
| | $ | 170,352 |
|
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