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				6 Months Ended
	Jun. 30, 2012 Power [Member]	Dec. 31, 2011 Power [Member]	Jun. 30, 2012 Rabbi Trust Fund [Member]	Jun. 30, 2012 Rabbi Trust Fund [Member] Power [Member] Debt Securities [Member]	Jun. 30, 2012 Nuclear Decommissioning Trust (NDT) Fund [Member]	Jun. 30, 2012 Nuclear Decommissioning Trust (NDT) Fund [Member] Power [Member] Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
After tax amount of net unrealized gains recognized in AOCI				$ 4		$ 88
Amount of other-than-temporary impairments					12
Accounts Receivable	21	27	1
Accounts Payable	$ 16	$ 22	$ 2