Derivative Instruments And Hedging Activities (Activity Of Energy Commodity Contracts Designated As Cash Flow Hedges) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Derivative Instruments And Hedging Activities [Abstract]
Amount of net pre-tax loss arising during the period included in accumulated other comprehensive loss			$ (1)
Effective portion of Fuel and Purchased Energy	13		27
Ineffective portion of Revenue		[1]		[1]
Total net pre-tax (gain) loss reclassified into income	13		27
Net pre-tax loss on commodity derivatives included in other comprehensive loss	$ 13		$ 26

[1] For the three months ended March 31, 2012 and 2011, no amounts were reclassified from AOCL to income because it was deemed probable that the forecasted hedged transactions would not occur.