Derivative Instruments And Hedging Activities (Activity Of Energy Commodity Contracts Designated As Cash Flow Hedges) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009
Derivative Instruments And Hedging Activities [Abstract]
Amount of net pre-tax loss arising during the period included in accumulated other comprehensive loss			$ (100)	$ (129)
Effective portion of Fuel and Purchased Energy	80		135	164
Ineffective portion of Revenue	1	[1]		2	[1]
Total net pre-tax (gain) loss reclassified into income	81		135	166
Net pre-tax loss on commodity derivatives included in other comprehensive loss	81		35	37
Derivative gain loss reclassified from AOCL to income	$ 1			$ 2

[1] Included in the above table is a loss of $1 million and $2 million for the years ended December 31, 2011 and 2009, respectively, which were reclassified from AOCL to income because the forecasted hedged transactions were deemed probable not to occur.