Related Party Transactions (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Related Party Transactions (Textual) [Abstract]
Cash distributions paid to members		$ 156	$ 121
Cash contributions received from members		0	13
Note receivable interest rate on EPB's cash management program		1.90%		2.00%
Equity method investee current other financing obligation		5		5
Severance costs	$ 1		$ 10