Derivative Instruments And Hedging Activities (Changes In The Fair Values Of Commodity Derivatives) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010
Derivatives, Fair Value [Line Items]
Total deferred gains	$ (4)	[1]	$ (4)	[1]
Total deferred losses	(210)	[1]	(302)	[1]
Net deferred losses	(214)	[1]	(306)	[1]
Unrealized gain/(loss) on derivatives, tax	(126)	[1]	(138)	[1]
Purchased Power Expense [Member]
Derivatives, Fair Value [Line Items]
Pre-tax gain/(loss) recognized in income	(78)	[1],[2]	(91)	[1],[3]
Unrealized gain/(loss) on derivatives, tax	11		56
Gas Purchased For Resale [Member]
Derivatives, Fair Value [Line Items]
Pre-tax gain/(loss) recognized in income	(18)	[1]	(9)	[1]
Non-Utility Revenue [Member]
Derivatives, Fair Value [Line Items]
Pre-tax gain/(loss) recognized in income	(30)	[1],[2]	(38)	[1],[3]
Unrealized gain/(loss) on derivatives, tax	(34)		(36)
Deferred Derivative Gains [Member]
Derivatives, Fair Value [Line Items]
Current-Deferred derivative gains	(3)	[1]	(5)	[1]
Regulatory Liabilities, Long Term [Member]
Derivatives, Fair Value [Line Items]
Current-Deferred derivative gains	(1)	[1]	1	[1]
Deferred Derivative Losses [Member]
Derivatives, Fair Value [Line Items]
Deferred derivative losses, current	26	[1]	(49)	[1]
Recoverable Energy Costs [Member]
Derivatives, Fair Value [Line Items]
Deferred derivative losses, current	(247)	[1]	(285)	[1]
Regulatory Assets, Long Term [Member]
Derivatives, Fair Value [Line Items]
Deferred gain/(loss), asset	$ 11	[1]	$ 32	[1]

[1] Qualifying derivative contracts, which have been designated as normal purchases or normal sales contracts, are not reported at fair value under the accounting rules for derivatives and hedging and, therefore, are excluded from the table.

[2] For the year ended December 31, 2011, Con Edison recorded in non-utility operating revenues and purchased power expense an unrealized pre-tax gain/(loss) of $(34) million and $11 million, respectively.

[3] For the year ended December 31, 2010, Con Edison recorded in non-utility operating revenues and purchased power expense an unrealized pre-tax gain/(loss) of $(36) million and $56 million, respectively.