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Rate and Regulatory Matters (Tables) | 12 Months Ended
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Dec. 31, 2016
Regulated Operations [Abstract] |
Schedule of regulatory assets |
|  | (Thousands of Dollars) |  |  |
|  | December 31, |  |  | Remaining
Regulatory Assets |  | 2016 |  |  | 2015 |  |  | Recovery Periods
Retirement Benefits |  | $ | 40,603 |  |  | $ | 39,378 |  |  | Various
Income Taxes |  |  | 15,899 |  |  |  | 15,541 |  |  | Various
Rate Cases, Tank Painting, and Other |  |  | 4,392 |  |  |  | 3,633 |  |  | 2-10 years
Total |  | $ | 60,894 |  |  | $ | 58,552 |  |  |

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- Definition Tabular disclosure of assets that are created when regulatory agencies permit public utilities to defer certain costs included in rate-setting to the balance sheet. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44264-110382 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 715 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501251&loc=d3e52485-110419 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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