Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Assets [Abstract]
Restricted cash	$ 45	$ 102
Accounts receivable	726	697
Securitized regulatory assets	369	413
Other assets	143	138
Total Assets	17,349	17,651
Liabilities [Abstract]
Current portion long-term debt, including, capital leases	466	443
Current regulatory liabilities	116	66
Securitization bonds	201	302
Other long term liabilities	104	103
Variable Interest Entity Securitization [Member]
Assets [Abstract]
Restricted cash	45	102
Accounts receivable	35	34
Securitized regulatory assets	369	413
Other assets	7	7
Total Assets	456	556
Liabilities [Abstract]
Accounts payable and accrued current liabilities	2	11
Current portion long-term debt, including, capital leases	189	177
Current regulatory liabilities	46	50
Securitization bonds	201	302
Other long term liabilities	8	7
Total Liabilities	$ 446	$ 547