| Schedule of Goodwill [Table Text Block] |
Changes in the carrying amount of goodwill by segment were as follows: | | | | | | | | | | | | | | | | | | Pipeline | | Storage | | Fuels Marketing | | Total | | (Thousands of Dollars) | Balances as of January 1, 2016 and December 31, 2016: | | | | | | | | Goodwill | $ | 306,207 |
| | $ | 691,220 |
| | $ | 53,255 |
| | $ | 1,050,682 |
| Accumulated impairment losses | — |
| | (331,913 | ) | | (22,132 | ) | | (354,045 | ) | Net goodwill | 306,207 |
| | 359,307 |
| | 31,123 |
| | 696,637 |
| | | | | | | | | Activity for the year ended December 31, 2017: | | | | | | | | Navigator Acquisition preliminary purchase price allocation (a) | 400,838 |
| | — |
| | — |
| | 400,838 |
| | | | | | | | | Balances as of December 31, 2017: | | | | | | | | Goodwill | 707,045 |
| | 691,220 |
| | 53,255 |
| | 1,451,520 |
| Accumulated impairment losses | — |
| | (331,913 | ) | | (22,132 | ) | | (354,045 | ) | Net goodwill | $ | 707,045 |
| | $ | 359,307 |
| | $ | 31,123 |
| | $ | 1,097,475 |
|
| | (a) | See Note 4 for discussion of the Navigator Acquisition. |
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