Available-For-Sale Securities (Fair Values And Gross Unrealized Gains And Losses For The Securities Held In The NDT Fund) (Details) (Nuclear Decommissioning Trust (NDT) Fund [Member], Power [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Equity Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Cost	$ 589	$ 582
Gross Unrealized Gains	187	126
Gross Unrealized Losses	(4)	(23)
Fair Value	772	685
Government Obligations [Member]
Schedule of Available-for-Sale Securities [Line Items]
Cost	314	343
Gross Unrealized Gains	10	16
Gross Unrealized Losses	(1)	0
Fair Value	323	359
Other Debt Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Cost	289	268
Gross Unrealized Gains	17	15
Gross Unrealized Losses	(1)	(2)
Fair Value	305	281
Total Debt Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Cost	603	611
Gross Unrealized Gains	27	31
Gross Unrealized Losses	(2)	(2)
Fair Value	628	640
Other Securities [Member]
Schedule of Available-for-Sale Securities [Line Items]
Cost	49	24
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	49	24
Total Debt Securities
Schedule of Available-for-Sale Securities [Line Items]
Cost	1,241	1,217
Gross Unrealized Gains	214	157
Gross Unrealized Losses	(6)	(25)
Fair Value	$ 1,449	$ 1,349