Available-For-Sale Securities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
	Aug. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains		$ 144	$ 119	$ 183
Nuclear Decommissioning Trust (NDT) Fund [Member]
Schedule of Available-for-sale Securities [Line Items]
Amount of other-than-temporary impairments		19
Nuclear Decommissioning Trust (NDT) Fund [Member] | Power [Member]
Schedule of Available-for-sale Securities [Line Items]
Decommissioning costs including contingencies		2.1
Decommissioning liability noncurrent		238
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		66
Rabbi Trust [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross realized gains	31	0	31	0
Amount of other-than-temporary impairments		$ 3