Derivative Instruments And Hedging Activities (Changes In The Fair Values Of Commodity Derivatives) (Details) (USD $) In Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010
Total deferred gains	$ (5)		$ 1		$ 4		$ (5)
Total deferred losses	(16)		66		(5)		(224)
Net deferred losses	(21)		67		(1)		(229)
Pre-tax gain/(loss) recognized in income	97		(52)		80		(95)
Other Current Liabilities [Member]
Current-Deferred derivative gains			1				(5)
Other Current Assets [Member]
Deferred gain/(loss), asset			95				(66)
Deferred Derivative Gains [Member]
Current-Deferred derivative gains	(4)				2
Regulatory Liabilities, Long Term [Member]
Total deferred gains	(1)				2
Deferred Derivative Losses [Member]
Deferred derivative losses, current	25				69
Recoverable Energy Costs [Member]
Deferred gain/(loss), asset	(53)		(80)		(102)		(135)
Regulatory Assets, Long Term [Member]
Deferred gain/(loss), asset	12		51		28		(23)
Purchased Power Expense [Member]
Pre-tax gain/(loss) recognized in income	73	[1]	(43)	[2]	52	[3]	(106)
Unrealized gain/(loss) on derivatives, tax	10		110		60
Gas Purchased for Resale [Member]
Pre-tax gain/(loss) recognized in income	17		(11)		11		(6)
Non-utility Revenue [Member]
Pre-tax gain/(loss) recognized in income	7	[1]	2	[2]	17	[3]	17	[4]
Unrealized gain/(loss) on derivatives, tax	$ (12)		$ (45)		$ (25)		$ 2

[1] For the three months ended June 30, 2011 Con Edison recorded in non-utility operating revenues and purchased power expense an unrealized pre-tax (loss)/gain of $(12) million and $10 million, respectively.

[2] For the three months ended June 30, 2010, Con Edison recorded in non-utility operating revenues and purchased power expense an unrealized pre-tax gain/(loss) of $(45) million and $110 million, respectively.

[3] For the six months ended June 30, 2011, Con Edison recorded in non-utility operating revenues and purchased power expense an unrealized pre-tax (loss)/gain of $(25) million and $60 million, respectively.

[4] For the six months ended June 30, 2010, Con Edison recorded in non-utility operating revenues an unrealized pre-tax gain/(loss) of $2 million.