Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 retail_customers sqmi	Mar. 31, 2014
Basis of Presentation [Abstract]
Increase (Decrease) in Inventories	$ 13	$ (2)
Service Area Sq Miles	4,000
Incorporated Cities	52
Number of Retail Customers	844,393
Service Area Population	1.8
Percent of State's Population	46.00%
Other Comprehensive Income	$ 0	$ 0