Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012		Dec. 31, 2012
Segment Financial Information
External revenues	$ 3,519		$ 3,755		$ 7,248		$ 7,743
Internal revenues	0		0		0		2
Total revenues	3,519	[1]	3,755	[1]	7,248	[1]	7,745	[1]
Depreciation and amortization	374		347		727		701
Investment income	(15)		13		3		24
Interest expense	256		274		514		520
Income taxes	(58)		127		58		349
NET INCOME (LOSS)	(164)		188		32		494
Total assets	50,157		48,048		50,157		48,048		50,406
Total goodwill	6,447		6,444		6,447		6,444		6,447
Property additions	586		394		1,412		911
Regulated Distribution
Segment Financial Information
External revenues	2,041		2,139		4,253		4,493
Internal revenues	0		0		0		0
Total revenues	2,041		2,139		4,253		4,493
Depreciation and amortization	220		208		422		425
Investment income	9		19		27		42
Interest expense	135		135		270		269
Income taxes	108		94		234		187
NET INCOME (LOSS)	179		158		389		317
Total assets	26,936		25,787		26,936		25,787
Total goodwill	5,025		5,025		5,025		5,025
Property additions	283		177		719		443
Regulated Transmission
Segment Financial Information
External revenues	180		184		356		370
Internal revenues	0		0		0		0
Total revenues	180		184		356		370
Depreciation and amortization	31		29		60		58
Investment income	0		1		0		1
Interest expense	22		23		45		46
Income taxes	30		30		61		66
NET INCOME (LOSS)	51		54		102		112
Total assets	4,797		4,473		4,797		4,473
Total goodwill	526		526		526		526
Property additions	97		59		186		122
Competitive Energy Services
Segment Financial Information
External revenues	1,377		1,501		2,791		3,020
Internal revenues	176		209		392		477
Total revenues	1,553		1,710		3,183		3,497
Depreciation and amortization	114		103		225		203
Investment income	(17)		6		(1)		12
Interest expense	61		71		134		136
Income taxes	(207)		14		(230)		97
NET INCOME (LOSS)	(339)		25		(377)		166
Total assets	17,910		17,216		17,910		17,216
Total goodwill	896		893		896		893
Property additions	185		132		468		303
Other/Corporate
Segment Financial Information
External revenues	(31)		(23)		(58)		(47)
Internal revenues	0		0		0		0
Total revenues	(31)		(23)		(58)		(47)
Depreciation and amortization	9		8		20		16
Investment income	2		1		3		1
Interest expense	38		45		65		69
Income taxes	7		(25)		(11)		(41)
NET INCOME (LOSS)	(52)		(41)		(82)		(69)
Total assets	514		572		514		572
Total goodwill	0		0		0		0
Property additions	21		26		39		43
Reconciling Adjustments
Segment Financial Information
External revenues	(48)		(46)		(94)		(93)
Internal revenues	(176)		(209)		(392)		(475)
Total revenues	(224)		(255)		(486)		(568)
Depreciation and amortization	0		(1)		0		(1)
Investment income	(9)		(14)		(26)		(32)
Interest expense	0		0		0		0
Income taxes	4		14		4		40
NET INCOME (LOSS)	(3)		(8)		0		(32)
Total assets	0		0		0		0
Total goodwill	0		0		0		0
Property additions	$ 0		$ 0		$ 0		$ 0

[1] Includes excise tax collections of $107 million in each of the three month periods ended June 30, 2013 and 2012 and $229 million and $228 million in the six months ended June 30, 2013 and 2012, respectively.