| 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, | | | 2020 | | 2019 | | 2020 | | 2019 | | | (Thousands of Dollars) | | Revenues: | | | | | | | | | | | | | | | | | Pipeline | $ | 176,210 | | | $ | 179,173 | | | $ | 537,999 | | | $ | 507,917 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Storage | 122,435 | | | 113,735 | | | 365,059 | | | 327,638 | | | | | | | | | | | Fuels marketing | 63,946 | | | 85,148 | | | 191,873 | | | 262,776 | | | | | | | | | | | | | | | | | | | | | | | | | | | Consolidation and intersegment eliminations | — | | | — | | | (9) | | | (4) | | | Total revenues | $ | 362,591 | | | $ | 378,056 | | | $ | 1,094,922 | | | $ | 1,098,327 | | | | | | | | | | | Operating income (loss): | | | | | | | | | Pipeline | $ | 83,821 | | | $ | 87,818 | | | $ | 32,878 | | | $ | 233,834 | | | Storage | 48,816 | | | 37,906 | | | 140,637 | | | 108,222 | | | Fuels marketing | (31) | | | 4,268 | | | 9,761 | | | 9,353 | | | Consolidation and intersegment eliminations | — | | | — | | | — | | | (32) | | | Total segment operating income | 132,606 | | | 129,992 | | | 183,276 | | | 351,377 | | | General and administrative expenses | 25,457 | | | 27,804 | | | 72,128 | | | 78,363 | | | Other depreciation and amortization expense | 2,105 | | | 2,216 | | | 6,462 | | | 6,154 | | | Total operating income | $ | 105,044 | | | $ | 99,972 | | | $ | 104,686 | | | $ | 266,860 | |
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| Reconciliation of Assets from Segment to Consolidated [Table Text Block] |
Total assets by reportable segment were as follows: | | | | | | | | | | | | | September 30, 2020 | | December 31, 2019 | | | (Thousands of Dollars) | | Pipeline | $ | 3,623,565 | | | $ | 3,884,819 | | | Storage | 2,033,196 | | | 2,082,832 | | | Fuels marketing | 24,636 | | | 31,064 | | | Total segment assets | 5,681,397 | | | 5,998,715 | | | | | | | Other partnership assets | 180,909 | | | 187,277 | | | Total consolidated assets | $ | 5,862,306 | | | $ | 6,185,992 | |
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