| Schedule of Segment Reporting Information, by Segment [Table Text Block] |
Results of operations for the reportable segments were as follows: | | | | | | | | | | | | | | | | | | Three Months Ended June 30, | | Six Months Ended June 30, | | 2014 | | 2013 | | 2014 | | 2013 | | (Thousands of Dollars) | Revenues: | | | | | | | | Pipeline | $ | 117,798 |
| | $ | 96,976 |
| | $ | 220,757 |
| | $ | 190,253 |
| Storage: | | | | | | | | Third parties | 138,296 |
| | 132,503 |
| | 262,650 |
| | 263,163 |
| Intersegment | 6,690 |
| | 8,245 |
| | 13,973 |
| | 18,021 |
| Related party | — |
| | 1,931 |
| | 929 |
| | 3,172 |
| Total storage | 144,986 |
| | 142,679 |
| | 277,552 |
| | 284,356 |
| Fuels marketing: | | | | | | | | Third parties | 493,651 |
| | 661,959 |
| | 1,114,622 |
| | 1,434,967 |
| Related party | — |
| | 8,645 |
| | — |
| | 8,645 |
| Total fuels marketing | 493,651 |
| | 670,604 |
| | 1,114,622 |
| | 1,443,612 |
| Consolidation and intersegment eliminations | (6,690 | ) | | (8,245 | ) | | (13,973 | ) | | (18,021 | ) | Total revenues | $ | 749,745 |
| | $ | 902,014 |
| | $ | 1,598,958 |
| | $ | 1,900,200 |
| | | | | | | | | Operating income: | | | | | | | | Pipeline | $ | 60,236 |
| | $ | 51,227 |
| | $ | 113,226 |
| | $ | 91,108 |
| Storage | 50,007 |
| | 44,412 |
| | 92,014 |
| | 98,368 |
| Fuels marketing | 4,821 |
| | 3,432 |
| | 14,379 |
| | 1,839 |
| Consolidation and intersegment eliminations | 7 |
| | 153 |
| | (10 | ) | | 1,259 |
| Total segment operating income | 115,071 |
| | 99,224 |
| | 219,609 |
| | 192,574 |
| General and administrative expenses | 23,163 |
| | 19,653 |
| | 44,019 |
| | 47,147 |
| Other depreciation and amortization expense | 2,554 |
| | 2,599 |
| | 5,133 |
| | 5,097 |
| Total operating income | $ | 89,354 |
| | $ | 76,972 |
| | $ | 170,457 |
| | $ | 140,330 |
|
|
| Reconciliation of Assets from Segment to Consolidated [Table Text Block] |
Total assets by reportable segment were as follows: | | | | | | | | | | June 30,
2014 | | December 31,
2013 | | (Thousands of Dollars) | Pipeline | $ | 1,839,264 |
| | $ | 1,797,698 |
| Storage | 2,265,630 |
| | 2,275,183 |
| Fuels marketing | 330,283 |
| | 445,882 |
| Total segment assets | 4,435,177 |
| | 4,518,763 |
| Other partnership assets | 460,602 |
| | 513,423 |
| Total consolidated assets | $ | 4,895,779 |
| | $ | 5,032,186 |
|
|