| 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, | | | | | 2020 | | 2019 | | 2020 | | 2019 | | | (Thousands of Dollars) | | | | | | | | Revenues: | | | | | | | | | | | | | | | | | Pipeline | $ | 166,108 | | | $ | 172,493 | | | $ | 361,789 | | | $ | 328,744 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Storage | 119,407 | | | 110,403 | | | 242,624 | | | 213,903 | | | | | | | | | | | Fuels marketing | 54,025 | | | 89,549 | | | 127,927 | | | 177,628 | | | | | | | | | | | | | | | | | | | | | | | | | | | Consolidation and intersegment eliminations | — | | | — | | | (9) | | | (4) | | | Total revenues | $ | 339,540 | | | $ | 372,445 | | | $ | 732,331 | | | $ | 720,271 | | | | | | | | | | | Operating income (loss): | | | | | | | | | Pipeline | $ | 71,981 | | | $ | 78,712 | | | $ | (50,943) | | | $ | 146,016 | | | Storage | 43,242 | | | 38,098 | | | 91,821 | | | 70,316 | | | Fuels marketing | 3,349 | | | 3,160 | | | 9,792 | | | 5,085 | | | Consolidation and intersegment eliminations | — | | | — | | | — | | | (32) | | | Total segment operating income | 118,572 | | | 119,970 | | | 50,670 | | | 221,385 | | | General and administrative expenses | 23,700 | | | 24,868 | | | 46,671 | | | 50,559 | | | Other depreciation and amortization expense | 2,171 | | | 1,819 | | | 4,357 | | | 3,938 | | | Total operating income (loss) | $ | 92,701 | | | $ | 93,283 | | | $ | (358) | | | $ | 166,888 | |
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| Reconciliation of Assets from Segment to Consolidated [Table Text Block] |
Total assets by reportable segment were as follows: | | | | | | | | | | | | | June 30, 2020 | | December 31, 2019 | | | (Thousands of Dollars) | | | | Pipeline | $ | 3,635,467 | | | $ | 3,884,819 | | | Storage | 2,032,327 | | | 2,082,832 | | | Fuels marketing | 23,357 | | | 31,064 | | | Total segment assets | 5,691,151 | | | 5,998,715 | | | | | | | Other partnership assets | 145,047 | | | 187,277 | | | Total consolidated assets | $ | 5,836,198 | | | $ | 6,185,992 | |
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