Derivative Instruments And Hedging Activities (Deferred Regulatory Assets Or Liabilities Reclassified To Income) (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Regulatory Clause Revenues, Under-Recovered [Member]
Net Unrealized Gain (Loss) Deferred as a Regulatory Liability (Asset)	$ 2	$ 5	$ 3
Net Realized Loss Recognized in Fuel and Purchased Energy Expense	(1)	(3)	(3)	(5)
Power Delivery [Member]
Net Unrealized Gain (Loss) Deferred as a Regulatory Liability (Asset)	2	7	9	1
Net Realized Loss Recognized in Fuel and Purchased Energy Expense	$ (4)	$ (6)	$ (11)	$ (13)