Risk Management and Fair Values (Derivative Instruments Designated as Cash Flow Hedges On Consolidated Statements Of Income) (Details) (Competitive Businesses Operating Revenues [Member], Electricity Swaps And Options [Member], Cash Flow Hedging [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Competitive Businesses Operating Revenues [Member] | Electricity Swaps And Options [Member] | Cash Flow Hedging [Member]
Effect of Derivative instruments designated as cash flow hedges on consolidated statements of income
Amount of gain (loss) recognized in AOCI (effective portion)	$ 81		$ (190)		$ 111
Amount of gain reclassified from accumulated OCI into income (effective portion)	$ (193)	[1]	$ 47	[1]	$ 268	[1]

[1] (a)Before taxes of ($68) million, $18 million, and $94 million, for the years ended December 31, 2014, 2013, and 2012, respectively