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Basis of Presentation (Details) $ in Millions | 9 Months Ended
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Sep. 30, 2017 USD ($) mi² retail_customers | Sep. 30, 2016 USD ($)
Basis of Presentation [Abstract] |  |
Service Area Sq Miles | mi² | 4,000 |
Incorporated Cities | 51 |
Number of Retail Customers | retail_customers | 873,000 |
Percent of State's Population | 46.00% |
Decoupling Mechanism Deferrals, Net | $ (15) | $ (4)
Defined Benefit Plan, Non-service Cost | $ 2 |

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- Definition The deferral, which can be either a positive or negaitive amount depending on whether a collection from or refund to customers results, of the amounts recorded in net income for energy useage by customers on a weather adjusted basis that is different from base rates as determined under the Company's decoupling mechanism, expected to be recovered or refunded in future periods. + References No definition available. + Details
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- Definition Number of incorporated cities in service area. + References No definition available. + Details
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- Definition Includes residential, commercial and industrial. + References No definition available. + Details
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- Definition Service area population as a percent of the state's population. + References No definition available. + Details
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- Definition Approximate square miles of service area. + References No definition available. + Details
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- Definition Amount of cost recognized for passage of time related to defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(2) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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