Organization and Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Assets [Abstract]
Cash and cash equivalents	$ 68	$ 65	$ 52	$ 86
Restricted cash	147	120
Accounts receivable	1,317	1,351
Other current assets	196	197
Property, plant and equipment	13,746	12,992
Securitized regulatory assets	577	729
Other assets	199	206
Total Assets	26,009	24,896
Liabilities [Abstract]
Current portion long-term debt, including, capital leases	526	925
Other current liabilities	549	597
Mortgage bonds, notes and other	6,405	6,114
Securitization bonds	479	643
Capital lease obligations	23	43
Other long term liabilities	331	358
Variable Interest Entity Securitization [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Restricted cash	107	104
Accounts receivable	34	42
Inventories	0	0
Other current assets	0	0
Property, plant and equipment	0	0
Securitized regulatory assets	577	729
Other assets	10	13
Total Assets	728	888
Liabilities [Abstract]
Accounts payable and accrued current liabilities	14	17
Current portion long-term debt, including, capital leases	164	150
Other current liabilities	55	62
Mortgage bonds, notes and other	0	0
Securitization bonds	479	643
Capital lease obligations	0	0
Other long term liabilities	7	6
Total Liabilities	719	878
Variable Interest Entity, Primary Beneficiary [Member]
Assets [Abstract]
Cash and cash equivalents	25	4
Restricted cash	7	8
Accounts receivable	17	8
Inventories	183	99
Other current assets	1	1
Property, plant and equipment	73	54
Securitized regulatory assets	0	0
Other assets	6	9
Total Assets	312	183
Liabilities [Abstract]
Accounts payable and accrued current liabilities	24	27
Current portion long-term debt, including, capital leases	7	7
Other current liabilities	0	6
Mortgage bonds, notes and other	30	35
Securitization bonds	0	0
Capital lease obligations	14	23
Other long term liabilities	2	7
Total Liabilities	77	105
Consolidated Variable Interest Entity [Member]
Assets [Abstract]
Cash and cash equivalents	25	4
Restricted cash	114	112
Accounts receivable	51	50
Inventories	183	99
Other current assets	1	1
Property, plant and equipment	73	54
Securitized regulatory assets	577	729
Other assets	16	22
Total Assets	1,040	1,071
Liabilities [Abstract]
Accounts payable and accrued current liabilities	38	44
Current portion long-term debt, including, capital leases	171	157
Other current liabilities	55	68
Mortgage bonds, notes and other	30	35
Securitization bonds	479	643
Capital lease obligations	14	23
Other long term liabilities	9	13
Total Liabilities	796	983
Variable Interest Entity Restricted [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Restricted cash	114	112
Accounts receivable	36	44
Inventories	0	0
Other current assets	0	0
Property, plant and equipment	23	38
Securitized regulatory assets	577	729
Other assets	16	21
Total Assets	766	944
Liabilities [Abstract]
Accounts payable and accrued current liabilities	14	18
Current portion long-term debt, including, capital leases	171	157
Other current liabilities	55	66
Mortgage bonds, notes and other	30	35
Securitization bonds	479	643
Capital lease obligations	14	23
Other long term liabilities	8	12
Total Liabilities	$ 771	$ 954