Basis of Presentation Basis of Presentation (Details) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2011 sqmi	Dec. 31, 2010
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