Related Party Transactions (Narrative) (Details) $ in Millions	1 Months Ended	3 Months Ended				5 Months Ended	9 Months Ended		12 Months Ended
	Feb. 28, 2014 USD ($)	Sep. 30, 2015 USD ($) Rating-Agencies-Downgrades	Jun. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) Rating-Agencies-Downgrades	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Related Party Transaction [Line Items]
Due from Affiliates		$ 9					$ 9
Advance to parent (Note 14)		6					6		$ 8
Advance to parent (Note 14)		3					3		7
Taxes Payable		607					607		626
Contractual Interest on Debt Classified as LSTC		522		$ 516		$ 874	1,554
Texas Competitive Electric Holdings [Member]
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction							15
Related Party Transaction, Sale of Assets To Related Party			$ 12	7	$ 24
Sponsor Group [Member]
Related Party Transaction [Line Items]
Selling, general and administrative expenses from transactions with related party				0				$ 10
Energy Future Holdings Corp. [Member]
Related Party Transaction [Line Items]
Intercompany payables		107					107		107
Interest expense, related party								2
Related Party Tax Expense, Due to Affiliates, Current		0							16
Related Party Transaction, Expenses from Transactions with Related Party							26	33
Oncor [Member]
Related Party Transaction [Line Items]
Related party transaction, amounts of transaction		279		281			739	746
Due to Affiliate		156					156		118
Pension Plan, Defined Benefit [Member]
Related Party Transaction [Line Items]
Defined Benefit Plan Contributions By Employer Excluding Affiliated Supplemental Plan	$ 84
Defined Benefit Plan, Contributions by Employer	20
Majority-Owned Subsidiary, Unconsolidated [Member] | Oncor [Member] | Pension Plan, Defined Benefit [Member]
Related Party Transaction [Line Items]
Defined Benefit Plan, Contributions by Employer	$ 64
Energy Future Holdings Corp. [Member] | Texas Competitive Electric Holdings [Member]
Related Party Transaction [Line Items]
Selling, general and administrative expenses from transactions with related party		52		47			$ 151	$ 147
Energy Future Holdings Corp. [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
LIBOR rate (as a percent)							5.00%	5.00%
Texas Competitive Electric Holdings Company LLC
Related Party Transaction [Line Items]
Contractual Interest on Debt Classified as LSTC		520		514		$ 871	$ 1,549
Texas Competitive Electric Holdings Company LLC | Oncor [Member]
Related Party Transaction [Line Items]
Delivery fee surcharge remitted to related party		5		5			13	$ 13
Event of credit rating downgrade, letter of credit required to be posted to secure payment obligations		$ 170					$ 170
Event of credit rating downgrade, minimum number of rating agencies downgrade below investment grade (in credit agencies downgrades) | Rating-Agencies-Downgrades		2					2
Texas Competitive Electric Holdings Company LLC | Senior Notes [Member]
Related Party Transaction [Line Items]
Long-term Debt Held by Affiliates		$ 382					$ 382		382
Texas Competitive Electric Holdings Company LLC | Decommisioning liablity [Member] | Oncor [Member]
Related Party Transaction [Line Items]
Due to Affiliate, Noncurrent		372					372		479
Texas Competitive Electric Holdings Company LLC | Collateral posted [Member] | Oncor [Member]
Related Party Transaction [Line Items]
Letter of credit posted as collateral		0					0		9
Texas Competitive Electric Holdings Company LLC | Related Party Transactions, Debt Held By Related Party [Member]
Related Party Transaction [Line Items]
Intercompany payables									382
Interest expense, related party				0			1	13
Contractual Interest on Debt Classified as LSTC				$ 9			28	$ 16
Texas Competitive Electric Holdings Company LLC | Related Party Transactions, Debt Held By Related Party [Member] | Senior Notes [Member] | Energy Future Holdings Corp. [Member]
Related Party Transaction [Line Items]
Intercompany payables		$ 284					$ 284		$ 284