Investment In Oncor Holdings (Oncor Holdings and Distributions from Oncor Holdings) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended				9 Months Ended		12 Months Ended			60 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011	Sep. 30, 2012 Oncor [Member]	Sep. 30, 2012 Oncor Holdings [Member]	Sep. 30, 2011 Oncor Holdings [Member]	Dec. 31, 2008 Oncor Holdings [Member]	Sep. 30, 2008 Oncor Holdings [Member] Cash_commitments	Sep. 30, 2008 Refunds to customers [Member] Oncor Holdings [Member] Customer_refunds	Sep. 30, 2012 Commitment for additional energy efficiency initiatives [Member] Oncor Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership (as a percent)				80.00%
Investment in unconsolidated subsidiary	$ 5,870		$ 5,720
Distributions of earnings from unconsolidated subsidiaries	100	64			100	64
Eligible distributions after accounting for regulatory restrictions					218
Goodwill impairment charge removal							860
Number of cash commitments (in cash commitments)								2
Cash commitment reserves									72
Cash commitment refund to customers									46
Number of customer refunds (in customer refunds)									1
Total commitment for additional energy efficiency initiatives										100
Cumulative spending related to additional commitment for energy efficiency initiatives										94
Cumulative spending related to additional commitment for energy efficiency initiatives after-tax										61
Available for distribution under the cumulative net income restriction					468
Ratio of debt to equity, debt (as a percent)					60.00%
Ratio of debt to equity, equity (as a percent)					40.00%
Ratio of regulatory capitalization, debt (as a percent)					58.50%
Ratio of regulatory capitalization, equity (as a percent)					41.50%
Available for distribution under the capital structure restriction					$ 218