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Basis of Presentation (Details) shares in Millions, $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2015 USD ($) mi² retail_customers shares | Sep. 30, 2014 USD ($) | Sep. 30, 2015 USD ($) mi² retail_customers shares | Sep. 30, 2014 USD ($)
Basis of Presentation [Abstract] |  |  |  |
Service Area Sq Miles | mi² | 4,000 |  | 4,000 |
Incorporated Cities | 52 |  | 52 |
Number of Retail Customers | retail_customers | 851,650 |  | 851,650 |
Service Area Population | shares | 1.8 |  | 1.8 |
Percent of State's Population | 46.00% |  | 46.00% |
Increase (Decrease) in Inventories |  |  | $ (12) | $ (18)
Other Comprehensive Income | $ 0 | $ 0 | $ 0 | $ 0

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