Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Assets [Abstract]
Restricted cash	$ 90	$ 102
Accounts receivable	789	697
Securitized regulatory assets	326	413
Other assets	144	138
Total Assets	17,501	17,651
Liabilities [Abstract]
Current portion long-term debt, including, capital leases	484	443
Current regulatory liabilities	144	66
Securitization bonds	201	302
Other long term liabilities	104	103
Variable Interest Entity Securitization [Member]
Assets [Abstract]
Restricted cash	90	102
Accounts receivable	39	34
Securitized regulatory assets	326	413
Other assets	6	7
Total Assets	461	556
Liabilities [Abstract]
Accounts payable and accrued current liabilities	9	11
Current portion long-term debt, including, capital leases	189	177
Current regulatory liabilities	45	50
Securitization bonds	201	302
Other long term liabilities	8	7
Total Liabilities	$ 452	$ 547