Financial Risk Management Activities (Schedule Of Derivative Instruments Not Designated As Hedging Instruments And Their Impact On Condensed Consolidated Statements Of Operations) (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized on derivatives not designated as hedging instruments	$ 13	$ (6)	$ (28)	$ (5)
Operating Revenues [Member] | Energy-Related Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized on derivatives not designated as hedging instruments	24	(6)	(18)	3
Energy Costs [Member] | Energy-Related Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized on derivatives not designated as hedging instruments	$ (11)	$ 0	$ (10)	$ (8)