Related-Party Transactions (Narrative) (Details) (USD $)			9 Months Ended	12 Months Ended	9 Months Ended		3 Months Ended			9 Months Ended			1 Months Ended	3 Months Ended					9 Months Ended		3 Months Ended		9 Months Ended							9 Months Ended						1 Months Ended		10 Months Ended					1 Months Ended		1 Months Ended				9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Energy Future Holdings Corp. [Member]	Dec. 31, 2011 Energy Future Holdings Corp. [Member]	Sep. 30, 2012 Related Party Transactions, Income Tax Payments [Member] Energy Future Holdings Corp. [Member]	Sep. 30, 2011 Related Party Transactions, Income Tax Payments [Member] Energy Future Holdings Corp. [Member]	Sep. 30, 2012 Energy Future Intermediate Holding CO LLC [Member] Related Party Transactions, Agreement Between Parties to Settle Obligations Under The Note [Member] Oncor [Member]	Sep. 30, 2012 Texas Competitive Electric Holdings Company LLC [Member] Oncor [Member]	Sep. 30, 2011 Texas Competitive Electric Holdings Company LLC [Member] Oncor [Member]	Sep. 30, 2012 Texas Competitive Electric Holdings Company LLC [Member] Oncor [Member]	Sep. 30, 2011 Texas Competitive Electric Holdings Company LLC [Member] Oncor [Member]	Dec. 31, 2011 Texas Competitive Electric Holdings Company LLC [Member] Oncor [Member]	Aug. 31, 2012 Texas Competitive Electric Holdings Company LLC [Member] Related Party Transactions, Agreement Between Parties To Settle Future Reimbursements [Member] Oncor [Member]	Sep. 30, 2012 Texas Competitive Electric Holdings Company LLC [Member] Related Party Transactions, Agreement Between Parties To Settle Future Reimbursements [Member] Oncor [Member]	Sep. 30, 2012 Texas Competitive Electric Holdings Company LLC [Member] Related Party Transactions, Decommisioning Liablity [Member] Oncor [Member]	Dec. 31, 2011 Texas Competitive Electric Holdings Company LLC [Member] Related Party Transactions, Decommisioning Liablity [Member] Oncor [Member]	Sep. 30, 2012 Texas Competitive Electric Holdings Company LLC [Member] Related Party Transactions, Collateral Posted [Member] Oncor [Member]	Dec. 31, 2011 Texas Competitive Electric Holdings Company LLC [Member] Related Party Transactions, Collateral Posted [Member] Oncor [Member]	Sep. 30, 2012 Energy Future Holdings Corp. [Member] Oncor Holdings or Oncor [Member]	Sep. 30, 2011 Energy Future Holdings Corp. [Member] Oncor Holdings or Oncor [Member]	Sep. 30, 2012 Energy Future Holdings Corp. [Member] Oncor [Member]	Sep. 30, 2011 Energy Future Holdings Corp. [Member] Oncor [Member]	Sep. 30, 2012 Energy Future Holdings Corp. [Member] Oncor [Member]	Sep. 30, 2011 Energy Future Holdings Corp. [Member] Oncor [Member]	Sep. 30, 2012 Energy Future Holdings Corp. [Member] Receivable Attributable to Income Taxes [Member] Oncor Holdings or Oncor [Member]	Dec. 31, 2011 Energy Future Holdings Corp. [Member] Receivable Attributable to Income Taxes [Member] Oncor Holdings or Oncor [Member]	Sep. 30, 2012 Line of Credit [Member] Energy Future Intermediate Holding CO LLC [Member] TCEH to EFH [Member]	Sep. 30, 2012 Line of Credit [Member] Indirect Guarantee of Indebtedness [Member] Energy Future Intermediate Holding CO LLC [Member] TCEH to EFH [Member]	Dec. 31, 2011 Line of Credit [Member] Indirect Guarantee of Indebtedness [Member] Energy Future Intermediate Holding CO LLC [Member] TCEH to EFH [Member]	Sep. 30, 2012 Secured Debt [Member] Energy Future Intermediate Holding CO LLC [Member] Goldman, Sachs & Co. [Member]	Sep. 30, 2012 Noninterest bearing note payable maturing in 2016 [Member] Texas Competitive Electric Holdings Company LLC [Member] Related Party Transactions, Agreement Between Parties to Settle Obligations Under The Note [Member] Oncor [Member]	Sep. 30, 2012 11.75% Senior Secured Second Lien Notes due March 1, 2022 [Member] Secured Debt [Member]	Dec. 31, 2011 11.75% Senior Secured Second Lien Notes due March 1, 2022 [Member] Secured Debt [Member]	Aug. 31, 2012 11.75% Senior Secured Second Lien Notes due March 1, 2022 [Member] Secured Debt [Member] Energy Future Intermediate Holding CO LLC [Member]	Feb. 29, 2012 11.75% Senior Secured Second Lien Notes due March 1, 2022 [Member] Secured Debt [Member] Energy Future Intermediate Holding CO LLC [Member]	Feb. 29, 2012 11.75% Senior Secured Second Lien Notes due March 1, 2022 [Member] Secured Debt [Member] Energy Future Intermediate Holding CO LLC [Member] Goldman, Sachs & Co. [Member]	Aug. 31, 2012 11.75% Senior Secured Second Lien Notes due March 1, 2022 [Member] Secured Debt [Member] Energy Future Intermediate Holding CO LLC [Member] Goldman, Sachs & Co. [Member]	Oct. 31, 2012 11.75% Senior Secured Second Lien Notes due March 1, 2022 [Member] Secured Debt [Member] Energy Future Intermediate Holding CO LLC [Member] Affiliates of KKR and TPG Management, L.P. [Member]	Sep. 30, 2012 6.875% Fixed Senior Secured First Lien Notes due August 15, 2017 [Member] Secured Debt [Member]	Dec. 31, 2011 6.875% Fixed Senior Secured First Lien Notes due August 15, 2017 [Member] Secured Debt [Member]	Aug. 31, 2012 6.875% Fixed Senior Secured First Lien Notes due August 15, 2017 [Member] Secured Debt [Member] Energy Future Intermediate Holding CO LLC [Member]	Aug. 31, 2012 6.875% Fixed Senior Secured First Lien Notes due August 15, 2017 [Member] Secured Debt [Member] Energy Future Intermediate Holding CO LLC [Member] Goldman, Sachs & Co. [Member]	Aug. 31, 2012 11.75% Senior Secured Second Lien Notes due March 1, 2022 and 6.875% Fixed Senior Secured First Lien Notes due August 15, 2017 [Member] Secured Debt [Member] Energy Future Intermediate Holding CO LLC [Member] Goldman, Sachs & Co. [Member]	Oct. 31, 2012 Issuance of Debt [Member] 6.875% Fixed Senior Secured First Lien Notes due August 15, 2017 [Member] Secured Debt [Member] Energy Future Intermediate Holding CO LLC [Member]	Oct. 31, 2012 Issuance of Debt [Member] 6.875% Fixed Senior Secured First Lien Notes due August 15, 2017 [Member] Secured Debt [Member] Energy Future Intermediate Holding CO LLC [Member] Goldman, Sachs & Co. [Member]	Oct. 31, 2012 Issuance of Debt [Member] 6.875% Fixed Senior Secured First Lien Notes due August 15, 2017 [Member] Secured Debt [Member] Energy Future Intermediate Holding CO LLC [Member] Affiliates of KKR and TPG Management, L.P. [Member]	Sep. 30, 2012 Minimum [Member] Texas Competitive Electric Holdings Company LLC [Member] Oncor [Member] Rating-Agencies-Downgrades	Sep. 30, 2012 Oncor [Member]	Sep. 30, 2012 Oncor [Member] Oncor Holdings [Member]	Sep. 30, 2011 Oncor [Member] Oncor Holdings [Member]
Related Party Transaction [Line Items]
Related Party Tax Expense, Due to Affiliates, Current			$ 1,000,000	$ 119,000,000																$ 89,000,000
Related Party Transaction, Expenses from Transactions with Related Party					172,000,000	30,000,000
Long-term debt, gross																												689,000,000	1,592,000,000			1,750,000,000	0						250,000,000	0
Due from Affiliates																											233,000,000
Maximum Borrowing Principal and Interest Note																											2,000,000,000
Debt Issuance Cost																														10,000,000													3,000,000
Debt Instrument, Face Amount																																		600,000,000	1,150,000,000	1,150,000,000	600,000,000				250,000,000	250,000,000		253,000,000		253,000,000
Related Party Transaction, Amounts of Transaction								281,000,000	309,000,000	746,000,000	798,000,000		159,000,000																							7,000,000		4,000,000							1,000,000
Percentage Of Equity Method Investment Consolidated Revenues Related To Services Provided To Entity																																																	29.00%	34.00%
Due to Affiliate								154,000,000		154,000,000		138,000,000
Related Party Transaction, Decrease in Member Interest, After Tax														2,000,000
Related Party Transaction, Decrease in Investment in Unconsolidated Subsidiary, Offsetting Decrease in Equity														1,000,000
Equity Method Investment, Ownership Percentage														80.00%																																		80.00%
Related Party, Remaining Interest To Be Paid																															53,000,000
Interest Expense, Related Party								2,000,000	8,000,000	16,000,000	24,000,000
Related Party Transaction, Remaining Balance at Settlement Date at Discount							159,000,000
Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party																					10,000,000	10,000,000	27,000,000	28,000,000
Public Utilities, Delivery Fee Surcharge Remitted To Related Party								5,000,000	5,000,000	12,000,000	13,000,000
Due to Affiliate, Noncurrent															286,000,000	225,000,000
Receivables from affiliates	224,000,000	86,000,000																							17,000,000
Due to Affiliate, Current																										2,000,000
Related Party Tax Expense, Due from Affiliates, Current																			27,000,000
Related Party, Letter of Credit Posted as Collateral																	11,000,000	12,000,000
Related Party, Event of Credit Rating Downgrade, Letter of Credit Required to be Posted to Secure Payment Obligations								$ 170,000,000		$ 170,000,000
Related Party, Event of Credit Rating Downgrade, Minimum Number of Rating Agencies Downgrade Below Investment Grade																																															2