Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Segment Financial Information
External revenues	$ 4,036		$ 4,052		$ 11,270		$ 11,778
Internal revenues	0		0		0		2
Total revenues	4,036	[1]	4,052	[1]	11,270	[1]	11,780	[1]
Depreciation and amortization	628		333		1,352		1,032
Investment income	5		39		8		63
Interest expense	257		230		771		750
Income taxes (benefits)	77		307		129		650
Income from continuing operations	209		422		233		908
Discontinued operations (Note 16)	9		3		17		11
NET INCOME (LOSS)	218		425		250		919
Total assets	50,383		48,738		50,383		48,738		50,406
Total goodwill	6,418		6,444		6,418		6,444		6,447
Property additions	548		775		1,960		1,686
Regulated Distribution
Segment Financial Information
External revenues	2,340		2,483		6,593		6,976
Internal revenues	0		0		0		0
Total revenues	2,340		2,483		6,593		6,976
Depreciation and amortization	460		193		882		618
Investment income	14		20		41		62
Interest expense	134		136		404		405
Income taxes (benefits)	50		168		284		355
Income from continuing operations	85		286		474		603
Discontinued operations (Note 16)	0		0		0		0
NET INCOME (LOSS)	85		286		474		603
Total assets	27,030		26,122		27,030		26,122
Total goodwill	5,025		5,025		5,025		5,025		5,025
Property additions	261		308		980		751
Regulated Transmission
Segment Financial Information
External revenues	190		187		546		557
Internal revenues	0		0		0		0
Total revenues	190		187		546		557
Depreciation and amortization	31		28		91		86
Investment income	0		0		0		1
Interest expense	23		24		68		70
Income taxes (benefits)	32		35		93		101
Income from continuing operations	54		59		156		171
Discontinued operations (Note 16)	0		0		0		0
NET INCOME (LOSS)	54		59		156		171
Total assets	4,953		4,519		4,953		4,519
Total goodwill	526		526		526		526
Property additions	105		47		291		169
Competitive Energy Services
Segment Financial Information
External revenues	1,573		1,462		4,350		4,465
Internal revenues	196		209		588		686
Total revenues	1,769		1,671		4,938		5,151
Depreciation and amortization	125		102		347		303
Investment income	(5)		36		(6)		48
Interest expense	53		73		187		209
Income taxes (benefits)	47		74		(189)		165
Income from continuing operations	68		126		(317)		284
Discontinued operations (Note 16)	9		3		17		11
NET INCOME (LOSS)	77		129		(300)		295
Total assets	17,809		16,846		17,809		16,846
Total goodwill	867		893		867		893		896
Property additions	162		412		630		715
Other/Corporate
Segment Financial Information
External revenues	(31)		(31)		(89)		(78)
Internal revenues	0		0		0		0
Total revenues	(31)		(31)		(89)		(78)
Depreciation and amortization	12		9		32		25
Investment income	3		(2)		6		(1)
Interest expense	47		(3)		112		66
Income taxes (benefits)	(44)		(8)		(55)		(49)
Income from continuing operations	0		0		0		0
Discontinued operations (Note 16)	0		0		0		0
NET INCOME (LOSS)	(10)		(13)		(92)		(82)
Total assets	591		1,251		591		1,251
Total goodwill	0		0		0		0
Property additions	20		8		59		51
Reconciling Adjustments
Segment Financial Information
External revenues	(36)		(49)		(130)		(142)
Internal revenues	(196)		(209)		(588)		(684)
Total revenues	(232)		(258)		(718)		(826)
Depreciation and amortization	0		1		0		0
Investment income	(7)		(15)		(33)		(47)
Interest expense	0		0		0		0
Income taxes (benefits)	(8)		38		(4)		78
Income from continuing operations	2		(49)		(80)		(150)
Discontinued operations (Note 16)	0		0		0		0
NET INCOME (LOSS)	12		(36)		12		(68)
Total assets	0		0		0		0
Total goodwill	0		0		0		0
Property additions	$ 0		$ 0		$ 0		$ 0

[1] Includes excise tax collections of $117 million and $123 million in the three months ended September 30, 2013 and 2012, respectively, and $346 million and $351 million in the nine months ended September 30, 2013 and 2012, respectively.