Related Party Transactions and Major Customers (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Related Party Transaction [Line Items]
Money Pool Borrowings	$ (3)								$ (3)
Investments (borrows) in Money Pool					433					433
Notes receivable from parent					750					750
Note receivable prime interest rate								3.25%
Interest Income (Expense) Net, Related Party									20	19	19
Corporate service charges									147	143	142
Revenues	644	745	656	532	585	748	676	531	2,577	2,540	2,337
Affiliates of NRG Energy, Inc. [Member]
Related Party Transaction [Line Items]
Revenues									658	648	594
Affiliates of Energy Future Holdings Corp. [Member]
Related Party Transaction [Line Items]
Revenues									167	162	182
Affiliates of Just Energy Group, Inc. [Member]
Related Party Transaction [Line Items]
Revenues									$ 126	$ 102	$ 81