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				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Rabbi Trust [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sales	$ 419	[1]	$ 13	[1]	$ 445	[1]	$ 77	[1]
Gross Realized Gains	2		0		4		4
Gross Realized Losses	(2)		0		(3)		(3)
Net Realized Gains (Losses)	0		0		1		1
Power [Member] | Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sales	221	[1]	220	[1]	779	[1]	837	[1]
Gross Realized Gains	45		35		101		95
Gross Realized Losses	(3)		(9)		(12)		(34)
Net Realized Gains (Losses)	$ 42		$ 26		$ 89		$ 61

[1] Includes activity in accounts related to the liquidation of funds being transitioned to new managers