Available-For-Sale Securities (Proceeds From The Sales Of And The Net Realized Gains On Securities in the NDT and Rabbi Trusts) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Rabbi Trust [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sales	$ 14	$ 47	$ 26	$ 64
Gross Realized Gains	0	4	2	4
Gross Realized Losses	(1)	(3)	(1)	(3)
Net Realized Gains (Losses)	(1)	1	1	1
Power [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sales	313	376	558	617
Gross Realized Gains	33	23	56	60
Gross Realized Losses	(5)	(6)	(9)	(25)
Net Realized Gains (Losses)	$ 28	$ 17	$ 47	$ 35