Available-For-Sale Securities (Proceeds From The Sales Of And The Net Realized Gains On Securities) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Nuclear Decommissioning Trust (NDT) Fund [Member] | Power [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sale and Maturity of Available-for-sale Securities	$ 1,070	$ 1,433	$ 1,355
Gross Realized Gains	112	153	144
Gross Realized Losses	(26)	(52)	(45)
Net Realized Gains (Losses)	86	101	99
Rabbi Trusts [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sale and Maturity of Available-for-sale Securities	89	233	0
Gross Realized Gains	4	6	0
Gross Realized Losses	(3)	0	0
Net Realized Gains (Losses)	$ 1	$ 6	$ 0