Financial Information By Business Segment (Financial Data For The Business Segments) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Segment Reporting Information [Line Items]
Depreciation and amortization	$ 884		$ 840		$ 791
Operating income	2,239		2,120		1,899
Income tax expense	600		548		440
O&R [Member]
Segment Reporting Information [Line Items]
Operating revenues	855		910		890
Depreciation and amortization	48		44		42
Operating income	114		108		92
Interest charges	34		35		29
Income tax expense	30		26		22
Total assets	2,485	[1]	2,348	[1]	2,187	[1]
Construction expenditures	111		135		127
Consolidation Adjustments [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	(96)		(91)		(90)
Total assets				[1]		[1]
Consolidated Edison Inc [Member]
Segment Reporting Information [Line Items]
Operating revenues	12,938		13,325		13,032
Depreciation and amortization	884		840		791
Operating income	2,239		2,120		1,899
Interest charges	594		609		611
Income tax expense	617		554		455
Total assets	39,214	[1]	36,348	[1]	33,844	[1]
Construction expenditures	2,003		2,029		2,194
Con Edison Development [Member]
Segment Reporting Information [Line Items]
All assets of the business segments	234
CECONY [Member]
Segment Reporting Information [Line Items]
Operating revenues	10,484		10,573		10,036
Depreciation and amortization	829		787		744
Operating income	2,083		1,922		1,716
Interest charges	534		549		553
Total assets	35,218	[1]	32,605	[1]	30,461	[1]
Construction expenditures	1,778		1,866		2,057
CECONY - Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	8,280		8,376		7,674
Inter-segment revenues	12		12		12
Depreciation and amortization	656		623		587
Operating income	1,695		1,549		1,368
Interest charges	414		424		425
Income tax expense	481		371		300
Total assets	27,123	[1]	25,045	[1]	23,309	[1]
Construction expenditures	1,354		1,421		1,596
CECONY - Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,521		1,541		1,701
Inter-segment revenues	5		5		5
Depreciation and amortization	110		102		98
Operating income	295		310		309
Interest charges	78		82		82
Income tax expense	43		91		90
Total assets	5,518	[1]	5,095	[1]	4,796	[1]
Construction expenditures	335		334		339
CECONY - Steam [Member]
Segment Reporting Information [Line Items]
Operating revenues	683		656		661
Inter-segment revenues	79		74		73
Depreciation and amortization	63		62		59
Operating income	93		63		39
Interest charges	42		43		46
Income tax expense	43		29		12
Total assets	2,577	[1]	2,465	[1]	2,356	[1]
Construction expenditures	89		111		122
O&R - Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	641		692	[1]	648	[1]
Depreciation and amortization	35		32	[1]	30	[1]
Operating income	81		74	[1]	64	[1]
Interest charges	20		22	[1]	18	[1]
Income tax expense	21		18	[1]	15	[1]
Total assets	1,755	[1]	1,630	[1]	1,525	[1]
Construction expenditures	79		99	[1]	85	[1]
O&R - Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	214		218		242
Depreciation and amortization	13		12		12
Operating income	33		34		28
Interest charges	12		12		9
Income tax expense	9		8		7
Total assets	722	[1]	686	[1]	627	[1]
Construction expenditures	32		36		42
O&R - Other [Member]
Segment Reporting Information [Line Items]
Operating revenues				[1]		[1]
Inter-segment revenues				[1]		[1]
Depreciation and amortization				[1]		[1]
Operating income				[1]
Interest charges	2	[1]	1	[1]	2	[1]
Income tax expense				[1]		[1]
Total assets	8	[1]	32	[1]	35	[1]
Construction expenditures				[1]		[1]
Competitive Energy Businesses [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,617		1,883		2,147
Inter-segment revenues	13		9
Depreciation and amortization	7		9		5
Operating income	46		97		93
Interest charges	(1)		(3)
Income tax expense	20		37		31
Total assets	856	[1]	828	[1]	751	[1]
Construction expenditures	114		28		10
Other Revenues And Eliminations In Segment Information [Member]
Segment Reporting Information [Line Items]
Operating revenues	(18)	[2]	(41)	[2]	(41)	[2]
Inter-segment revenues	(13)	[2]	(9)	[2]		[2]
Depreciation and amortization				[2]		[2]
Operating income	(4)	[2]	(7)	[2]	(3)	[2]
Interest charges	27	[2]	28	[2]	29	[2]
Income tax expense				[2]		[2]
Total assets	655	[1],[2]	567	[1],[2]	445	[1],[2]
Construction expenditures				[2]		[2]

[1] Includes amounts related to the RECO securitization.

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