Related Party Transactions and Major Customers (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		1 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Affiliates of NRG Energy, Inc. [Member]	Jun. 30, 2012 Affiliates of NRG Energy, Inc. [Member]	Jun. 30, 2013 Affiliates of NRG Energy, Inc. [Member]	Jun. 30, 2012 Affiliates of NRG Energy, Inc. [Member]	Jun. 30, 2013 Affiliates of Energy Future Holdings Corp. [Member]	Jun. 30, 2012 Affiliates of Energy Future Holdings Corp. [Member]	Jun. 30, 2013 Affiliates of Energy Future Holdings Corp. [Member]	Jun. 30, 2012 Affiliates of Energy Future Holdings Corp. [Member]	Aug. 31, 2013 Intercompany note payable
Related Party Transaction [Line Items]
Investments in Money Pool	$ 0		$ 0		$ 433
Notes Receivable from Parent	750		750		750
Interest Income (Expense) Net, Related Party	4	4	9	9
Corporate service charges	37	35	73	72
Sales to major customers						148	153	291	293	37	38	73	74
Debt Instrument, Interest Rate Terms														0.04
Extinguishment of Debt, Amount														$ 92