Related Party Transactions and Major Customers (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Related Party Transaction [Line Items]
Investments in Money Pool	$ 78		$ 78
Money Pool Borrowings					(3)
Interest Income (Expense) Net, Related Party	1	4	(1)	9
Corporate service charges	39	37	76	73
Sales to major customers	698	656	1,328	1,188
Affiliates of NRG Energy, Inc. [Member]
Related Party Transaction [Line Items]
Sales to major customers	164	148	330	291
Affiliates of Energy Future Holdings Corp. [Member]
Related Party Transaction [Line Items]
Sales to major customers	$ 41	$ 37	$ 81	$ 73