Investment In Oncor Holdings (Oncor Holdings Financial Statements) (Details) (Variable Interest Entity, Primary Beneficiary [Member], Oncor Holdings [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Variable Interest Entity, Primary Beneficiary [Member] | Oncor Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Operating revenues	$ 925	$ 897	$ 2,536	$ 2,359
Operation and maintenance expenses	(292)	(281)	(873)	(799)
Depreciation and amortization	(201)	(190)	(577)	(540)
Taxes other than income taxes	(113)	(107)	(313)	(297)
Other income	6	8	20	23
Other deductions	(1)	(2)	(4)	(7)
Interest income	3	7	24	25
Interest expense and related charges	(96)	(89)	(279)	(265)
Income before income taxes	231	243	534	499
Income tax expense	(95)	(101)	(221)	(204)
Net income	136	142	313	295
Net income attributable to noncontrolling interests	(27)	(29)	(64)	(60)
Net income attributable to Oncor Holdings	109	113	249	235
Current assets:
Cash and cash equivalents	9		9		12
Restricted cash	64		64		57
Trade accounts receivable — net	375		375		303
Trade accounts and other receivables from affiliates	154		154		179
Inventories	72		72		71
Accumulated deferred income taxes	39		39		73
Prepayments and other current assets	74		74		74
Total current assets	787		787		769
Restricted cash	16		16		16
Receivable from TCEH related to nuclear plant decommissioning	286		286		225
Other investments	78		78		73
Property, plant and equipment - net	11,191		11,191		10,569
Goodwill	4,064		4,064		4,064
Note receivable due from TCEH	0		0		138
Regulatory assets — net	1,542		1,542		1,505
Other noncurrent assets	77		77		73
Total assets	18,041		18,041		17,432
Current liabilities:
Short-term borrowings	784		784		392
Long-term debt due currently	123		123		494
Trade accounts payable — nonaffiliates	111		111		197
Income taxes payable to EFH Corp.	17		17		2
Accrued taxes other than income	130		130		151
Accrued interest	91		91		108
Other current liabilities	110		110		112
Total current liabilities	1,366		1,366		1,456
Accumulated deferred income taxes	1,750		1,750		1,688
Investment tax credits	25		25		28
Long-term debt, less amounts due currently	5,440		5,440		5,144
Other noncurrent liabilities and deferred credits	1,944		1,944		1,832
Total liabilities	$ 10,525		$ 10,525		$ 10,148