Derivative Instruments And Hedging Activities (Changes In The Fair Values Of Commodity Derivatives) (Details) (USD $) In Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Derivatives, Fair Value [Line Items]
Total deferred gains	$ (1)	[1]			$ 3	[1]
Total deferred losses	(53)	[1]			(59)	[1]
Net deferred losses	(54)	[1]	(130)	[1]	(56)	[1]	(359)	[1]
Pre-tax gain/(loss) recognized in income	40	[1]	(23)	[1]	120	[1]	(118)	[1]
Unrealized gain/(loss) on derivatives, tax					(9)
Derivative Asset [Member]
Derivatives, Fair Value [Line Items]
Total deferred losses			(127)	[1]			(351)	[1]
Derivative Liability [Member]
Derivatives, Fair Value [Line Items]
Total deferred losses			(3)	[1]			(8)	[1]
Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Current-Deferred derivative gains			(3)	[1]			(8)	[1]
Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Deferred gain/(loss), asset			(61)	[1]			(127)	[1]
Deferred Derivative Gains [Member]
Derivatives, Fair Value [Line Items]
Current-Deferred derivative gains	(2)	[1]
Regulatory Liabilities, Long Term [Member]
Derivatives, Fair Value [Line Items]
Total deferred gains	1	[1]			3	[1]
Deferred Derivative Losses [Member]
Derivatives, Fair Value [Line Items]
Deferred derivative losses, current	12	[1]			80	[1]
Recoverable Energy Costs [Member]
Derivatives, Fair Value [Line Items]
Deferred gain/(loss), asset	(75)	[1]	(70)	[1]	(177)	[1]	(205)	[1]
Regulatory Assets, Long Term [Member]
Derivatives, Fair Value [Line Items]
Deferred gain/(loss), asset	10	[1]	4	[1]	38	[1]	(19)	[1]
Purchased Power Expense [Member]
Derivatives, Fair Value [Line Items]
Pre-tax gain/(loss) recognized in income	29	[1],[2]	(26)	[1],[3]	81	[1],[4]	(132)	[1],[5]
Unrealized gain/(loss) on derivatives, tax	(1)		(34)		59		(34)
Gas Purchased For Resale [Member]
Derivatives, Fair Value [Line Items]
Pre-tax gain/(loss) recognized in income	6	[1]	(1)	[1]	17	[1]	(7)	[1]
Non-Utility Revenue [Member]
Derivatives, Fair Value [Line Items]
Pre-tax gain/(loss) recognized in income	5	[1],[2]	4	[1],[3]	22	[1],[4]	21	[1],[5]
Unrealized gain/(loss) on derivatives, tax	$ (10)		$ (3)		$ (35)		$ (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 three months ended September 30, 2011 Con Edison recorded in non-utility operating revenues and purchased power expense an unrealized pre-tax (loss) of $(10) million and $(1) million, respectively.

[3] For the three months ended September 30, 2010, Con Edison recorded in non-utility operating revenues and purchased power expense an unrealized pre-tax gain/(loss) of $(3)million and $(34) million, respectively.

[4] For the nine months ended September 30, 2011, Con Edison recorded in non-utility operating revenues and purchased power expense an unrealized pre-tax (loss)/gain of $(35) million and $59 million, respectively.

[5] For the nine months ended September 30, 2010, Con Edison recorded in non-utility operating revenues and purchased power expense an unrealized pre-tax gain/(loss) of $(1) million and $(34) million, respectively.