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Basis of Presentation Basis of Presentation (Details) (USD $) In Millions, except Share data, unless otherwise specified | Dec. 31, 2011 sqmi | Dec. 31, 2010
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Basis of Presentation [Abstract] |  |
Incorporated Cities | 52 |
Service Area Sq Miles | 4,000 |
Number of Retail Customers | 822,466 |
Service area population | 1,700,000 |
Percent of State's Population | 44.00% |
Entity Number of Employees | 2,634 |
Number of Union Employees | 840 |
Number of Union Employees Subject to Agreement A | 804 |
Number of Union Employees Subject to Agreement B | 36 |
Other Accrued Liabilities, Current |  | $ 67

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