Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Assets [Abstract]
Restricted cash	$ 102	$ 127
Accounts receivable	697	709
Securitized regulatory assets	413	577
Other assets	138	142
Total Assets	17,651	17,493
Liabilities [Abstract]
Other current liabilities	166	230
Current portion long-term debt, including, capital leases	443	470
Securitization bonds	302	479
Other long term liabilities	103	115
Variable Interest Entity Securitization [Member]
Assets [Abstract]
Restricted cash	102	107
Accounts receivable	34	34
Securitized regulatory assets	413	577
Other assets	7	10
Total Assets	556	728
Liabilities [Abstract]
Accounts payable and accrued current liabilities	11	14
Other current liabilities	50	55
Current portion long-term debt, including, capital leases	177	164
Securitization bonds	302	479
Other long term liabilities	7	7
Total Liabilities	$ 547	$ 719