Organization and Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Assets [Abstract]
Cash and cash equivalents	$ 57	$ 68	$ 197	$ 65
Restricted cash	86	147
Accounts receivable	1,262	1,317
Other current assets	187	196
Property, plant and equipment	13,924	13,746
Securitized regulatory assets	536	577
Other assets	188	199
Total Assets	25,846	26,009
Liabilities [Abstract]
Current portion long-term debt, including, capital leases	530	526
Other current liabilities	424	549
Mortgage bonds, notes and other	6,404	6,405
Securitization bonds	391	479
Capital lease obligations	18	23
Other long-term liabilities	295	331
Variable Interest Entity Securitization [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Restricted cash	46	107
Accounts receivable	34	34
Inventories	0	0
Other current assets	0	0
Property, plant and equipment	0	0
Securitized regulatory assets	536	577
Other assets	9	10
Total Assets	625	728
Liabilities [Abstract]
Accounts payable and accrued current liabilities	3	14
Current portion long-term debt, including, capital leases	168	164
Other current liabilities	48	55
Mortgage bonds, notes and other	0	0
Securitization bonds	391	479
Capital lease obligations	0	0
Other long-term liabilities	7	7
Total Liabilities	617	719
Variable Interest Entity, Primary Beneficiary [Member]
Assets [Abstract]
Cash and cash equivalents	12	25
Restricted cash	6	7
Accounts receivable	16	17
Inventories	106	183
Other current assets	2	1
Property, plant and equipment	72	73
Securitized regulatory assets	0	0
Other assets	6	6
Total Assets	220	312
Liabilities [Abstract]
Accounts payable and accrued current liabilities	32	24
Current portion long-term debt, including, capital leases	8	7
Other current liabilities	0	0
Mortgage bonds, notes and other	28	30
Securitization bonds	0	0
Capital lease obligations	12	14
Other long-term liabilities	2	2
Total Liabilities	82	77
Consolidated Variable Interest Entity [Member]
Assets [Abstract]
Cash and cash equivalents	12	25
Restricted cash	52	114
Accounts receivable	50	51
Inventories	106	183
Other current assets	2	1
Property, plant and equipment	72	73
Securitized regulatory assets	536	577
Other assets	15	16
Total Assets	845	1,040
Liabilities [Abstract]
Accounts payable and accrued current liabilities	35	38
Current portion long-term debt, including, capital leases	176	171
Other current liabilities	48	55
Mortgage bonds, notes and other	28	30
Securitization bonds	391	479
Capital lease obligations	12	14
Other long-term liabilities	9	9
Total Liabilities	699	796
Variable Interest Entity Restricted [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Restricted cash	52	114
Accounts receivable	36	36
Inventories	0	0
Other current assets	0	0
Property, plant and equipment	22	23
Securitized regulatory assets	536	577
Other assets	15	16
Total Assets	661	766
Liabilities [Abstract]
Accounts payable and accrued current liabilities	3	14
Current portion long-term debt, including, capital leases	176	171
Other current liabilities	48	55
Mortgage bonds, notes and other	28	30
Securitization bonds	391	479
Capital lease obligations	12	14
Other long-term liabilities	8	8
Total Liabilities	$ 666	$ 771