Organization and Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Assets [Abstract]
Cash and cash equivalents	$ 59	$ 68	$ 46	$ 65
Restricted cash	69	147
Accounts receivable	1,164	1,317
Other current assets	244	196
Property, plant and equipment	14,404	13,746
Securitized regulatory assets	456	577
Other assets	190	199
Total Assets	25,909	26,009
Liabilities [Abstract]
Current portion long-term debt, including, capital leases	633	526
Other current liabilities	479	549
Mortgage bonds, notes and other	6,526	6,405
Securitization bonds	302	479
Capital lease obligations	12	23
Other long-term liabilities	302	331
Variable Interest Entity Securitization [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Restricted cash	50	107
Accounts receivable	39	34
Inventories	0	0
Other current assets	0	0
Property, plant and equipment	0	0
Securitized regulatory assets	456	577
Other assets	8	10
Total Assets	553	728
Liabilities [Abstract]
Accounts payable and accrued current liabilities	3	14
Current portion long-term debt, including, capital leases	177	164
Other current liabilities	55	55
Mortgage bonds, notes and other	0	0
Securitization bonds	302	479
Capital lease obligations	0	0
Other long-term liabilities	7	7
Total Liabilities	544	719
Variable Interest Entity, Primary Beneficiary [Member]
Assets [Abstract]
Cash and cash equivalents	4	25
Restricted cash	5	7
Accounts receivable	10	17
Inventories	144	183
Other current assets	3	1
Property, plant and equipment	65	73
Securitized regulatory assets	0	0
Other assets	6	6
Total Assets	237	312
Liabilities [Abstract]
Accounts payable and accrued current liabilities	0	24
Current portion long-term debt, including, capital leases	8	7
Other current liabilities	0	0
Mortgage bonds, notes and other	26	30
Securitization bonds	0	0
Capital lease obligations	11	14
Other long-term liabilities	1	2
Total Liabilities	46	77
Consolidated Variable Interest Entity [Member]
Assets [Abstract]
Cash and cash equivalents	4	25
Restricted cash	55	114
Accounts receivable	49	51
Inventories	144	183
Other current assets	3	1
Property, plant and equipment	65	73
Securitized regulatory assets	456	577
Other assets	14	16
Total Assets	790	1,040
Liabilities [Abstract]
Accounts payable and accrued current liabilities	3	38
Current portion long-term debt, including, capital leases	185	171
Other current liabilities	55	55
Mortgage bonds, notes and other	26	30
Securitization bonds	302	479
Capital lease obligations	11	14
Other long-term liabilities	8	9
Total Liabilities	590	796
Variable Interest Entity Restricted [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Restricted cash	55	114
Accounts receivable	40	36
Inventories	0	0
Other current assets	0	0
Property, plant and equipment	20	23
Securitized regulatory assets	456	577
Other assets	14	16
Total Assets	585	766
Liabilities [Abstract]
Accounts payable and accrued current liabilities	3	14
Current portion long-term debt, including, capital leases	185	171
Other current liabilities	55	55
Mortgage bonds, notes and other	26	30
Securitization bonds	302	479
Capital lease obligations	11	14
Other long-term liabilities	7	8
Total Liabilities	$ 589	$ 771