Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011		Dec. 31, 2011
Segment Financial Information
External revenues	$ 4,311		$ 4,707		$ 12,256		$ 12,299
Internal revenues	0		12		2		56
Total revenues	4,311	[1]	4,719	[1]	12,258	[1]	12,355	[1]
Depreciation and amortization	343		419		1,057		1,153
Investment income	39		48		63		100
Net interest charges	212		250		696		708
Income taxes	309		325		658		550
Net income	425		530		919		770
Total assets	48,738		48,673		48,738		48,673		47,326
Total goodwill	6,444		6,428		6,444		6,428		6,441
Property additions	775		500		1,686		1,464
Regulated Distribution
Segment Financial Information
External revenues	2,438		2,864		6,857		7,496
Internal revenues	0		1		0		1
Total revenues	2,438		2,865		6,857		7,497
Depreciation and amortization	202		273		636		746
Investment income	20		28		62		76
Net interest charges	132		133		396		389
Income taxes	168		164		355		322
Net income	286	[2]	280		603	[2]	547
Total assets	26,122		26,802		26,122		26,802
Total goodwill	5,025		5,025		5,025		5,025
Property additions	308		234		751		615
Regulated Transmission
Segment Financial Information
External revenues	187		181		557		476
Internal revenues	0		0		0		0
Total revenues	187		181		557		476
Depreciation and amortization	28		31		89		81
Investment income	0		0		1		0
Net interest charges	22		23		68		64
Income taxes	35		32		101		79
Net income	59		56		171		136
Total assets	4,519		4,246		4,519		4,246
Total goodwill	526		526		526		526
Property additions	47		80		169		250
Competitive Energy Services
Segment Financial Information
External revenues	1,719		1,714		4,942		4,450
Internal revenues	210		315		686		976
Total revenues	1,929		2,029		5,628		5,426
Depreciation and amortization	105		110		307		307
Investment income	36		28		48		49
Net interest charges	62		73		175		195
Income taxes	76		142		173		163
Net income	129		242		295		278
Total assets	16,846		16,809		16,846		16,809
Total goodwill	893		877		893		877
Property additions	412		186		715		543
Other/Corporate
Segment Financial Information
External revenues	(30)		(40)		(78)		(93)
Internal revenues	0		0		0		0
Total revenues	(30)		(40)		(78)		(93)
Depreciation and amortization	8		5		25		19
Investment income	(1)		0		(1)		1
Net interest charges	(4)		21		57		60
Income taxes	(9)		(23)		(49)		(53)
Net income	(11)		(40)		(82)		(145)
Total assets	1,251		816		1,251		816
Total goodwill	0		0		0		0
Property additions	8		0		51		56
Reconciling Adjustments
Segment Financial Information
External revenues	(3)		(12)		(22)		(30)
Internal revenues	(210)		(304)		(684)		(921)
Total revenues	(213)		(316)		(706)		(951)
Depreciation and amortization	0		0		0		0
Investment income	(16)		(8)		(47)		(26)
Net interest charges	0		0		0		0
Income taxes	39		10		78		39
Net income	(38)		(8)		(68)		(46)
Total assets	0		0		0		0
Total goodwill	0		0		0		0
Property additions	$ 0		$ 0		$ 0		$ 0

[1] Includes excise tax collections of $123 million and $137 million in the three months ended September 30, 2012 and 2011, respectively, and $351 million and $371 million in the nine months ended September 30, 2012 and 2011, respectively.

[2] Regulated Distribution net income for the three and nine months ended September 30, 2012, include adjustments of $21.8 million and $15.1 million, respectively, from capitalizing various construction activities of the Allegheny Utilities that were previously expensed. The effect of these adjustments was not material to the current or previous periods.