Membership Interests (Changes in Membership Interests) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012		Sep. 30, 2011
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance			$ 5,805		$ 5,193
Net income	118	160	308		367
Distributions paid to parent			(950)
Effect of debt push-down from EFH Corp. (Note 4)			30		220
Capital contributions					30	[1]
Net effect of Oncor's settlement of reimbursement agreements with TCEH			(1)
Net effects of investment in long-term debt of affiliates (Note 3)			272		56
Net effects of cash flow hedges - Oncor			2	[2]	(24)	[3]
Other			(1)
Balance	5,465	5,842	5,465		5,842
Capital Accounts [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance			5,790		5,195
Net income			308		367
Distributions paid to parent			(950)
Effect of debt push-down from EFH Corp. (Note 4)			30		220
Capital contributions					30	[1]
Net effect of Oncor's settlement of reimbursement agreements with TCEH			(1)
Other			(1)
Balance	5,176	5,812	5,176		5,812
Accumulated Other Comprehensive Income [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance			15		(2)
Net effect of Oncor's settlement of reimbursement agreements with TCEH			0
Net effects of investment in long-term debt of affiliates (Note 3)			272		56
Net effects of cash flow hedges - Oncor			2	[2]	(24)	[3]
Other			0
Balance	$ 289	$ 30	$ 289		$ 30

[1] Reflects noncash settlement of certain income taxes payable arising as a result of the sale of equity interests in Oncor.

[2] Represents recognition in equity in earnings of unconsolidated subsidiary of previous losses on interest rate hedge transactions entered into by Oncor.

[3] Represents losses on interest rate hedge transactions entered into by Oncor.