Financial Information By Business Segment (Financial Data For The Business Segments) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012		Jun. 30, 2011
Segment Reporting Information [Line Items]
Depreciation and amortization			$ 469		$ 437
Operating income	475	398	1,036		1,024
CECONY
Segment Reporting Information [Line Items]
Operatin revenues	2,309	2,416	4,870		5,125
Depreciation and amortization	221	205	439		410
Operating income	380	370	925		917
O&R [Member]
Segment Reporting Information [Line Items]
Operatin revenues	164	178	374		419
Depreciation and amortization	13	12	26		24
Operating income	17	15	55		53
Consolidated Edison Inc
Segment Reporting Information [Line Items]
Operatin revenues	2,771	2,993	5,849		6,342
Depreciation and amortization	236	219	469		437
Operating income	475	398	1,036		1,024
CECONY - Electric [Member]
Segment Reporting Information [Line Items]
Operatin revenues	1,961	2,013	3,696		3,734
Inter-segment revenues	4	3	7		6
Depreciation and amortization	175	162	348		324
Operating income	348	350	573		566
CECONY - Gas [Member]
Segment Reporting Information [Line Items]
Operatin revenues	265	296	828		959
Inter-segment revenues	2	1	3		2
Depreciation and amortization	30	27	59		54
Operating income	54	31	275		237
CECONY - Steam [Member]
Segment Reporting Information [Line Items]
Operatin revenues	83	107	346		432
Inter-segment revenues	19	20	38		40
Depreciation and amortization	16	16	32		32
Operating income	(22)	(11)	77		114
Consolidation, Eliminations [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	(25)	(24)	(48)		(48)
O&R - Electric [Member]
Segment Reporting Information [Line Items]
Operatin revenues	129	141	257		289
Depreciation and amortization	9	8	19		17
Operating income	16	14	24		25
O&R - Gas [Member]
Segment Reporting Information [Line Items]
Operatin revenues	35	37	117		130
Depreciation and amortization	4	4	7		7
Operating income	1	1	31		28
Competitive Energy Businesses [Member]
Segment Reporting Information [Line Items]
Operatin revenues	300	406	610		814
Inter-segment revenues	2	2	4		5
Depreciation and amortization	2	2	4		3
Operating income	78	14	59		58
Other [Member]
Segment Reporting Information [Line Items]
Operatin revenues	(2)	(7)	(5)	[1]	(16)	[1]
Inter-segment revenues	(2)	(2)	(4)	[1]	(5)	[1]
Operating income		$ (1)	$ (3)	[1]	$ (4)	[1]

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