| Schedule of Segment Reporting Information, by Segment [Table Text Block] |
Results of operations for the reportable segments were as follows: | | | | | | | | | | | | | | | | | | Three Months Ended
September 30, | | Nine Months Ended
September 30, | | 2014 | | 2013 | | 2014 | | 2013 | | (Thousands of Dollars) | Revenues: | | | | | | | | Pipeline | $ | 125,461 |
| | $ | 111,508 |
| | $ | 346,218 |
| | $ | 301,761 |
| Storage: | | | | | | | | Third parties | 137,771 |
| | 130,227 |
| | 400,421 |
| | 393,390 |
| Intersegment | 6,174 |
| | 6,890 |
| | 20,147 |
| | 24,911 |
| Related party | — |
| | 1,491 |
| | 929 |
| | 4,663 |
| Total storage | 143,945 |
| | 138,608 |
| | 421,497 |
| | 422,964 |
| Fuels marketing: | | | | | | | | Third parties | 531,190 |
| | 534,919 |
| | 1,645,812 |
| | 1,969,886 |
| Related party | — |
| | — |
| | — |
| | 8,645 |
| Total fuels marketing | 531,190 |
| | 534,919 |
| | 1,645,812 |
| | 1,978,531 |
| Consolidation and intersegment eliminations | (6,174 | ) | | (6,890 | ) | | (20,147 | ) | | (24,911 | ) | Total revenues | $ | 794,422 |
| | $ | 778,145 |
| | $ | 2,393,380 |
| | $ | 2,678,345 |
| | | | | | | | | Operating income: | | | | | | | | Pipeline | $ | 65,652 |
| | $ | 58,018 |
| | $ | 178,878 |
| | $ | 149,126 |
| Storage | 49,401 |
| | 41,051 |
| | 141,415 |
| | 139,419 |
| Fuels marketing | 7,518 |
| | (9,079 | ) | | 21,897 |
| | (7,240 | ) | Consolidation and intersegment eliminations | (25 | ) | | 123 |
| | (35 | ) | | 1,382 |
| Total segment operating income | 122,546 |
| | 90,113 |
| | 342,155 |
| | 282,687 |
| General and administrative expenses | 24,967 |
| | 18,831 |
| | 68,986 |
| | 65,978 |
| Other depreciation and amortization expense | 2,481 |
| | 2,531 |
| | 7,614 |
| | 7,628 |
| Total operating income | $ | 95,098 |
| | $ | 68,751 |
| | $ | 265,555 |
| | $ | 209,081 |
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| Reconciliation of Assets from Segment to Consolidated [Table Text Block] |
Total assets by reportable segment were as follows: | | | | | | | | | | September 30,
2014 | | December 31,
2013 | | (Thousands of Dollars) | Pipeline | $ | 1,898,684 |
| | $ | 1,797,698 |
| Storage | 2,237,537 |
| | 2,275,183 |
| Fuels marketing | 306,636 |
| | 445,882 |
| Total segment assets | 4,442,857 |
| | 4,518,763 |
| Other partnership assets | 434,510 |
| | 513,423 |
| Total consolidated assets | $ | 4,877,367 |
| | $ | 5,032,186 |
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