Segment Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Segment Financial Information
External revenues	$ 16,191,000,000		$ 13,265,000,000		$ 12,956,000,000
Internal revenues	67,000,000		74,000,000		17,000,000
Total revenues	16,258,000,000	[1]	13,339,000,000	[1]	12,973,000,000	[1]
Depreciation and amortization	1,450,000,000		1,490,000,000		1,776,000,000
Investment income	114,000,000		117,000,000		204,000,000
Net interest charges	(1,008,000,000)		(845,000,000)		(978,000,000)
Income taxes	574,000,000		462,000,000		184,000,000
Net income (loss)	869,000,000		718,000,000		856,000,000
Total assets	47,326,000,000		35,531,000,000		35,054,000,000
Total goodwill	6,441,000,000		5,575,000,000		5,575,000,000
Property additions	2,278,000,000		1,963,000,000		2,203,000,000
Regulated Distribution
Segment Financial Information
External revenues	10,004,000,000		9,571,000,000		10,916,000,000
Internal revenues	0		139,000,000		0
Total revenues	10,004,000,000		9,710,000,000		10,916,000,000
Depreciation and amortization	943,000,000		1,145,000,000		1,432,000,000
Investment income	110,000,000		102,000,000		141,000,000
Net interest charges	(573,000,000)		(500,000,000)		(478,000,000)
Income taxes	335,000,000		338,000,000		243,000,000
Net income (loss)	570,000,000		553,000,000		335,000,000
Total assets	27,477,000,000		22,160,000,000		22,663,000,000
Total goodwill	5,551,000,000		5,551,000,000		5,551,000,000
Property additions	1,066,000,000		681,000,000		718,000,000
Competitive Energy Services
Segment Financial Information
External revenues	5,936,000,000		3,575,000,000		1,928,000,000
Internal revenues	1,237,000,000		2,301,000,000		2,843,000,000
Total revenues	7,173,000,000		5,876,000,000		4,771,000,000
Depreciation and amortization	415,000,000		284,000,000		279,000,000
Investment income	56,000,000		51,000,000		121,000,000
Net interest charges	(298,000,000)		(232,000,000)		(174,000,000)
Income taxes	222,000,000		128,000,000		305,000,000
Net income (loss)	377,000,000		210,000,000		446,000,000
Total assets	16,796,000,000		11,320,000,000		10,668,000,000
Total goodwill	890,000,000		24,000,000		24,000,000
Property additions	927,000,000		1,159,000,000		1,412,000,000
Regulated Independent Transmission
Segment Financial Information
External revenues	391,000,000		242,000,000		223,000,000
Internal revenues	0		0		0
Total revenues	391,000,000		242,000,000		223,000,000
Depreciation and amortization	66,000,000		47,000,000		50,000,000
Investment income	0		0		0
Net interest charges	(46,000,000)		(22,000,000)		(19,000,000)
Income taxes	66,000,000		32,000,000		26,000,000
Net income (loss)	112,000,000		54,000,000		39,000,000
Total assets	2,436,000,000		1,064,000,000		974,000,000
Total goodwill	0		0		0
Property additions	192,000,000		64,000,000		32,000,000
Other/Corporate
Segment Financial Information
External revenues	(114,000,000)		(88,000,000)		(82,000,000)
Internal revenues	0		0		0
Total revenues	(114,000,000)		(88,000,000)		(82,000,000)
Depreciation and amortization	26,000,000		14,000,000		15,000,000
Investment income	1,000,000		(2,000,000)		4,000,000
Net interest charges	(91,000,000)		(104,000,000)		(345,000,000)
Income taxes	(87,000,000)		(44,000,000)		(140,000,000)
Net income (loss)	(149,000,000)		(79,000,000)		(209,000,000)
Total assets	617,000,000		987,000,000		749,000,000
Total goodwill	0		0		0
Property additions	93,000,000		59,000,000		41,000,000
Reconciling Adjustments
Segment Financial Information
External revenues	(26,000,000)		(35,000,000)		(29,000,000)
Internal revenues	(1,170,000,000)		(2,366,000,000)		(2,826,000,000)
Total revenues	(1,196,000,000)		(2,401,000,000)		(2,855,000,000)
Depreciation and amortization	0		0		0
Investment income	(53,000,000)		(34,000,000)		(62,000,000)
Net interest charges	0		13,000,000		38,000,000
Income taxes	38,000,000		8,000,000		(250,000,000)
Net income (loss)	(41,000,000)		(20,000,000)		245,000,000
Total assets	0		0		0
Total goodwill	0		0		0
Property additions	$ 0		$ 0		$ 0

[1] Includes $486 million, $428 million and $395 million of excise tax collections in 2011, 2010 and 2009, respectively.