Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011		Dec. 31, 2011
Segment Financial Information
External revenues	$ 3,869		$ 4,048		$ 7,945		$ 7,592
Internal revenues	0		12		2		44
Total revenues	3,869	[1]	4,060	[1]	7,947	[1]	7,636	[1]
Depreciation and amortization	354		377		714		734
Investment income	13		31		24		52
Net interest charges	255		245		484		458
Income taxes	127		114		349		225
Net income	188		193		494		240
Total assets	48,048		47,596		48,048		47,596		47,326
Total goodwill	6,444		6,436		6,444		6,436		6,441
Property additions	412		569		1,001		1,018
Regulated Distribution
Segment Financial Information
External revenues	2,095		2,409		4,420		4,632
Internal revenues	0		0		0		0
Total revenues	2,095		2,409		4,420		4,632
Depreciation and amortization	215		232		435		473
Investment income	19		25		42		48
Net interest charges	132		134		264		256
Income taxes	94		100		187		158
Net income	161		171		318		267
Total assets	25,787		25,069		25,787		25,069
Total goodwill	5,025		5,025		5,025		5,025
Property additions	177		266		443		381
Regulated Transmission
Segment Financial Information
External revenues	184		182		370		295
Internal revenues	0		0		0		0
Total revenues	184		182		370		295
Depreciation and amortization	29		28		61		50
Investment income	0		0		1		0
Net interest charges	22		24		45		41
Income taxes	31		33		66		47
Net income	52		57		112		80
Total assets	4,473		4,202		4,473		4,202
Total goodwill	526		526		526		526
Property additions	59		81		122		170
Competitive Energy Services
Segment Financial Information
External revenues	1,616		1,495		3,222		2,736
Internal revenues	209		318		477		661
Total revenues	1,825		1,813		3,699		3,397
Depreciation and amortization	103		109		203		197
Investment income	6		16		12		21
Net interest charges	59		69		113		122
Income taxes	14		12		97		21
Net income	25		21		166		36
Total assets	17,216		17,146		17,216		17,146
Total goodwill	893		885		893		885
Property additions	150		197		393		411
Other/Corporate
Segment Financial Information
External revenues	(24)		(30)		(47)		(53)
Internal revenues	0		0		0		0
Total revenues	(24)		(30)		(47)		(53)
Depreciation and amortization	8		8		16		14
Investment income	1		0		1		1
Net interest charges	42		19		63		39
Income taxes	(25)		(30)		(41)		(30)
Net income	(42)		(51)		(69)		(105)
Total assets	572		1,179		572		1,179
Total goodwill	0		0		0		0
Property additions	26		25		43		56
Reconciling Adjustments
Segment Financial Information
External revenues	(2)		(8)		(20)		(18)
Internal revenues	(209)		(306)		(475)		(617)
Total revenues	(211)		(314)		(495)		(635)
Depreciation and amortization	(1)		0		(1)		0
Investment income	(13)		(10)		(32)		(18)
Net interest charges	0		(1)		(1)		0
Income taxes	13		(1)		40		29
Net income	(8)		(5)		(33)		(38)
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 and $116 million in the three months ended June 30, 2012 and 2011, respectively, and $228 million and $235 million in the six months ended June 30, 2012 and 2011, respectively.