Financial Information By Business Segment - Financial Data for the Business Segments (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Segment Reporting Information [Line Items]
Depreciation and amortization					$ 709		$ 659
Operating income	851		756		1,886		1,781
CECONY [Member]
Segment Reporting Information [Line Items]
Operating revenues	2,868		2,917		7,738		8,042
Depreciation and amortization	225		209		664		618
Operating income	754		702		1,678		1,619
O&R [Member]
Segment Reporting Information [Line Items]
Operating revenues	226		241		601		660
Depreciation and amortization	13		12		39		36
Operating income	44		38		100		91
Consolidated Edison Inc [Member]
Segment Reporting Information [Line Items]
Operating revenues	3,438		3,629		9,287		9,972
Depreciation and amortization	240		222		709		659
Operating income	851		756		1,886		1,781
CECONY - Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	2,611		2,644		6,307		6,378
Inter-segment revenues	4		3		11		9
Depreciation and amortization	179		166		527		489
Operating income	812		758		1,383		1,326
CECONY - Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	189		197		1,017		1,156
Inter-segment revenues	1		1		4		4
Depreciation and amortization	31		28		89		82
Operating income	(21)		(23)		255		212
CECONY - Steam [Member]
Segment Reporting Information [Line Items]
Operating revenues	68		76		414		508
Inter-segment revenues	20		20		58		59
Depreciation and amortization	15		15		48		47
Operating income	(37)		(33)		40		81
Consolidation Adjustments [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	(25)		(24)		(73)		(72)
O&R - Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	199		217		457		507
Depreciation and amortization	10		9		28		26
Operating income	50		44		74		69
O&R - Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	27		24		144		153
Depreciation and amortization	3		3		11		10
Operating income	(6)		(6)		26		22
Competitive Energy Businesses [Member]
Segment Reporting Information [Line Items]
Operating revenues	344		472		954		1,286
Inter-segment revenues	2		3		6		9
Depreciation and amortization	2		1		6		5
Operating income	53		16		111		75
Other Revenues And Eliminations In Segment Information [Member]
Segment Reporting Information [Line Items]
Operating revenues			(1)	[1]	(6)	[1]	(16)	[1]
Inter-segment revenues	(2)	[1]	(3)	[1]	(6)	[1]	(9)	[1]
Operating income					$ (3)	[1]	$ (4)	[1]

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