Financial Information By Business Segment (Financial Data For The Business Segments) (Details) (USD $) In Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Operating revenues	$ 3,629		$ 3,707		$ 9,972		$ 10,185
Depreciation and amortization	222		211		659		626
Operating income	756		705		1,781		1,627
CECONY - Electric [Member]
Operating revenues	2,644		2,570		6,378		6,402
Inter-segment revenues	3		3		9		9
Depreciation and amortization	166		156		489		464
Operating income	758		715		1,326		1,228
CECONY - Gas [Member]
Operating revenues	197		204		1,156		1,126
Inter-segment revenues	1		1		4		4
Depreciation and amortization	28		26		82		76
Operating income	(23)		(16)		212		243
CECONY - Steam [Member]
Operating revenues	76		91		508		487
Inter-segment revenues	20		18		59		55
Depreciation and amortization	15		16		47		46
Operating income	(33)		(33)		81		41
O&R - Electric [Member]
Operating revenues	217		245		507		559
Depreciation and amortization	9		8		26		24
Operating income	44		52		69		71
O&R - Gas [Member]
Operating revenues	24		25		153		150
Depreciation and amortization	3		3		10		9
Operating income	(6)		(4)		22		20
Competitive Energy Businesses [Member]
Operating revenues	472		584		1,286		1,491
Inter-segment revenues	3		2		9		6
Depreciation and amortization	1		2		5		7
Operating income	16		(8)		75		25
Other Revenues And Eliminations In Segment Information [Member]
Operating revenues	(1)	[1]	(12)	[1]	(16)	[1]	(30)	[1]
Inter-segment revenues	(3)	[1]	(2)	[1]	(9)	[1]	(6)	[1]
Operating income			(1)	[1]	(2)	[1]	(1)	[1]
CECONY [Member]
Operating revenues	2,917		2,865		8,042		8,015
Depreciation and amortization	209		198		618		586
Operating income	702		666		1,619		1,512
Consolidation Adjustments [Member]
Inter-segment revenues	(24)		(22)		(72)		(68)
O&R [Member]
Operating revenues	241		270		660		709
Depreciation and amortization	12		11		36		33
Operating income	$ 38		$ 48		$ 91		$ 91

[1] Parent company expenses, primarily interest, and consolidation adjustments. Other does not represent a business segment.