Basis of Presentation (Details) $ in Millions	12 Months Ended
	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2015 mi² shares
Basis of Presentation [Abstract]
Incorporated Cities						52
Service Area Sq Miles | mi²						4,000
Number of Retail Customers						852,164
Service area population						1,800,000
Percent of State's Population						46.00%
Entity Number of Employees						2,646
Number of Union Employees						764
Number of Union Employees Subject to Agreement A						713
Number of Union Employees Subject to Agreement B						51
revenue overstatment | $	$ 9	$ 3	$ 3	$ 2	$ 1