Financial Information By Business Segment (Financial Data For The Business Segments) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Segment Reporting Information [Line Items]
Depreciation and amortization	$ 233		$ 218
Operating income	561		626
CECONY [Member]
Segment Reporting Information [Line Items]
Operating revenues	2,561		2,709
Depreciation and amortization	218		204
Operating income	544		546
O&R [Member]
Segment Reporting Information [Line Items]
Operating revenues	210		241
Depreciation and amortization	13		12
Operating income	38		38
Consolidated Edison Inc [Member]
Segment Reporting Information [Line Items]
Operating revenues	3,078		3,349
Depreciation and amortization	233		218
Operating income	561		626
CECONY - Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,735		1,721
Inter-segment revenues	3		3
Depreciation and amortization	173		161
Operating income	224		217
CECONY - Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	563		663
Inter-segment revenues	1		1
Depreciation and amortization	29		27
Operating income	221		204
CECONY - Steam [Member]
Segment Reporting Information [Line Items]
Operating revenues	263		325
Inter-segment revenues	19		20
Depreciation and amortization	16		16
Operating income	99		125
Consolidation Adjustments [Member]
Segment Reporting Information [Line Items]
Inter-segment revenues	(23)		(24)
O&R - Electric [Member]
Segment Reporting Information [Line Items]
Operating revenues	128		149
Depreciation and amortization	9		9
Operating income	8		10
O&R - Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues	82		92
Depreciation and amortization	4		3
Operating income	30		28
Competitive Energy Businesses [Member]
Segment Reporting Information [Line Items]
Operating revenues	310		408
Inter-segment revenues	2		3
Depreciation and amortization	2		2
Operating income	(20)		44
Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	(3)	[1]	(9)	[1]
Inter-segment revenues	(2)	[1]	(3)	[1]
Operating income	$ (1)	[1]	$ (2)	[1]

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