Equity and Noncontrolling Interests (Table) (2 Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Equity And Noncontrolling Interests [Abstract]
EPB	$ 55	$ 25	$ 161	$ 75
Preferred Stock of Cheyenne Plains	5	5	15	15
Preferred Stock of Ruby	15	11	50	11
Net income attributable to noncontrolling interests	$ 75	$ 41	$ 226	$ 101