Derivative Instruments And Hedging Activities (Activity Of Energy Commodity Contracts Designated As Cash Flow Hedges) (Details) (USD $) In Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Derivative Instruments And Hedging Activities
Amount of net pre-tax gain (loss) arising during the period included in accumulated other comprehensive loss			$ (38)		$ 2		$ (116)
Effective portion of Fuel and Purchased Energy	15		23		61		108
Ineffective portion of Revenue	1	[1]			1	[1]	2	[1]
Total net pre-tax loss reclassified into income	16	[1]	23	[1]	62	[1]	110	[1]
Net pre-tax loss on commodity derivatives included in other comprehensive loss	16		(15)		64		(6)
Derivative gain loss reclassified from AOCL to income	$ 1

[1] For the three and nine months ended September 30, 2011, $1 million was reclassified from AOCL to income because the forecasted hedged transactions were deemed probable not to occur. For the three and nine months ended September 30, 2010, no amounts were reclassified from AOCL to income because the forecasted hedged transactions were deemed probable not to occur.