Net of tax amount of the appreciation (loss) in value of unsold available-for-sale securities attributable to the parent entity. Excludes amounts related to other than temporary impairment (OTTI) losses.

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+ Details

Available-For-Sale Securities (Narrative) (Detail) (USD $) In Millions, unless otherwise specified				9 Months Ended		1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2012 Power [Member]	Dec. 31, 2011 Power [Member]	Sep. 30, 2012 Rabbi Trust Fund [Member]	Sep. 30, 2012 Rabbi Trust Fund [Member] Power [Member] Debt Securities [Member]	Sep. 30, 2012 Nuclear Decommissioning Trust (NDT) Fund [Member]	Sep. 30, 2012 Nuclear Decommissioning Trust (NDT) Fund [Member] Power [Member]	Sep. 30, 2012 Nuclear Decommissioning Trust (NDT) Fund [Member] Power [Member]	Sep. 30, 2011 Nuclear Decommissioning Trust (NDT) Fund [Member] Power [Member]	Sep. 30, 2012 Nuclear Decommissioning Trust (NDT) Fund [Member] Power [Member]	Sep. 30, 2011 Nuclear Decommissioning Trust (NDT) Fund [Member] Power [Member]	Sep. 30, 2012 Nuclear Decommissioning Trust (NDT) Fund [Member] Power [Member] Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross Realized Gains						$ 59	$ 94	$ 26	$ 136	$ 121
After tax amount of net unrealized gains recognized in AOCI				5							77
Amount of other-than-temporary impairments					14
Accounts Receivable	61	27	4
Accounts Payable	$ 80	$ 22	$ 5