Organization and Basis of Presentation (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Assets [Abstract]
Cash and cash equivalents	$ 185	$ 68	$ 61	$ 65
Restricted cash	110	147
Accounts receivable	1,239	1,317
Other current assets	162	196
Property, plant and equipment	14,152	13,746
Securitized regulatory assets	497	577
Other assets	189	199
Total Assets	26,075	26,009
Liabilities [Abstract]
Current portion long-term debt, including, capital leases	848	526
Other current liabilities	508	549
Mortgage bonds, notes and other	6,528	6,405
Securitization bonds	391	479
Capital lease obligations	13	23
Other long-term liabilities	297	331
Variable Interest Entity Securitization [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Restricted cash	92	107
Accounts receivable	37	34
Inventories	0	0
Other current assets	0	0
Property, plant and equipment	0	0
Securitized regulatory assets	497	577
Other assets	9	10
Total Assets	635	728
Liabilities [Abstract]
Accounts payable and accrued current liabilities	12	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	626	719
Variable Interest Entity, Primary Beneficiary [Member]
Assets [Abstract]
Cash and cash equivalents	18	25
Restricted cash	7	7
Accounts receivable	16	17
Inventories	151	183
Other current assets	3	1
Property, plant and equipment	70	73
Securitized regulatory assets	0	0
Other assets	6	6
Total Assets	271	312
Liabilities [Abstract]
Accounts payable and accrued current liabilities	40	24
Current portion long-term debt, including, capital leases	8	7
Other current liabilities	0	0
Mortgage bonds, notes and other	27	30
Securitization bonds	0	0
Capital lease obligations	12	14
Other long-term liabilities	2	2
Total Liabilities	89	77
Consolidated Variable Interest Entity [Member]
Assets [Abstract]
Cash and cash equivalents	18	25
Restricted cash	99	114
Accounts receivable	53	51
Inventories	151	183
Other current assets	3	1
Property, plant and equipment	70	73
Securitized regulatory assets	497	577
Other assets	15	16
Total Assets	906	1,040
Liabilities [Abstract]
Accounts payable and accrued current liabilities	52	38
Current portion long-term debt, including, capital leases	176	171
Other current liabilities	48	55
Mortgage bonds, notes and other	27	30
Securitization bonds	391	479
Capital lease obligations	12	14
Other long-term liabilities	9	9
Total Liabilities	715	796
Variable Interest Entity Restricted [Member]
Assets [Abstract]
Cash and cash equivalents	0	0
Restricted cash	99	114
Accounts receivable	39	36
Inventories	0	0
Other current assets	0	0
Property, plant and equipment	21	23
Securitized regulatory assets	497	577
Other assets	15	16
Total Assets	671	766
Liabilities [Abstract]
Accounts payable and accrued current liabilities	13	14
Current portion long-term debt, including, capital leases	176	171
Other current liabilities	48	55
Mortgage bonds, notes and other	27	30
Securitization bonds	391	479
Capital lease obligations	12	14
Other long-term liabilities	8	8
Total Liabilities	$ 675	$ 771