Organization and Basis of Presentation (Consolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
ASSETS
Cash and cash equivalents	$ 230	$ 48	$ 75	$ 52
Restricted cash	21	120
Accounts receivable	1,251	1,504
Property, plant and equipment, net	17,576	16,820
Securitized regulatory assets	0	34
Total Assets	28,350	27,974
Liabilities [Abstract]
Current portion long-term debt, including capital leases	467	274
Current regulatory liabilities	78	153
Mortgage bonds, notes and other	8,346	7,860
Capital lease obligations	9	3
Variable Interest Entity, Primary Beneficiary [Member]
ASSETS
Cash and cash equivalents	12	7
Restricted cash	5	104
Accounts receivable	17	41
Inventories	40	67
Property, plant and equipment, net	70	81
Securitized regulatory assets	0	34
Other current and long-term assets	5	7
Total Assets	149	341
Liabilities [Abstract]
Accounts payable and accrued current liabilities	11	11
Current portion long-term debt, including capital leases	9	115
Current regulatory liabilities	0	32
Mortgage bonds, notes and other	13	15
Capital lease obligations	0	3
Other current and long-term liabilities	6	15
Total Liabilities	$ 39	191
Variable Interest Entity, Primary Beneficiary Securitization [Member]
ASSETS
Cash and cash equivalents		0
Restricted cash		96
Accounts receivable		26
Inventories		0
Property, plant and equipment, net		0
Securitized regulatory assets		34
Other current and long-term assets		1
Total Assets		157
Liabilities [Abstract]
Accounts payable and accrued current liabilities		3
Current portion long-term debt, including capital leases		105
Current regulatory liabilities		32
Mortgage bonds, notes and other		0
Capital lease obligations		0
Other current and long-term liabilities		9
Total Liabilities		149
Variable Interest Entity, Primary Beneficiary Other [Member]
ASSETS
Cash and cash equivalents		7
Restricted cash		8
Accounts receivable		15
Inventories		67
Property, plant and equipment, net		81
Securitized regulatory assets		0
Other current and long-term assets		6
Total Assets		184
Liabilities [Abstract]
Accounts payable and accrued current liabilities		8
Current portion long-term debt, including capital leases		10
Current regulatory liabilities		0
Mortgage bonds, notes and other		15
Capital lease obligations		3
Other current and long-term liabilities		6
Total Liabilities		$ 42