Financial Information by Business Segment (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 3,228	$ 3,156
Depreciation and amortization	329	297
Operating income/(loss)	771	642
Clean Energy Businesses
Segment Reporting Information [Line Items]
Depreciation and amortization	17	9
Operating income/(loss)	15	(51)
Con Edison Transmission
Segment Reporting Information [Line Items]
Operating income/(loss)	(3)	0
CECONY
Segment Reporting Information [Line Items]
Revenues	2,856	2,632
Depreciation and amortization	294	272
Operating income/(loss)	705	640
CECONY | Electric
Segment Reporting Information [Line Items]
Depreciation and amortization	229	213
Operating income/(loss)	292	273
CECONY | Gas
Segment Reporting Information [Line Items]
Depreciation and amortization	44	38
Operating income/(loss)	292	253
CECONY | Steam
Segment Reporting Information [Line Items]
Depreciation and amortization	21	21
Operating income/(loss)	121	114
O&R
Segment Reporting Information [Line Items]
Depreciation and amortization	17	17
Operating income/(loss)	53	53
O&R | Electric
Segment Reporting Information [Line Items]
Depreciation and amortization	12	12
Operating income/(loss)	14	18
O&R | Gas
Segment Reporting Information [Line Items]
Depreciation and amortization	5	5
Operating income/(loss)	39	35
Operating segment
Segment Reporting Information [Line Items]
Revenues	3,228	3,156
Operating segment | Clean Energy Businesses
Segment Reporting Information [Line Items]
Revenues	136	310
Operating segment | CECONY
Segment Reporting Information [Line Items]
Revenues	2,856	2,632
Operating segment | CECONY | Electric
Segment Reporting Information [Line Items]
Revenues	1,793	1,773
Operating segment | CECONY | Gas
Segment Reporting Information [Line Items]
Revenues	765	601
Operating segment | CECONY | Steam
Segment Reporting Information [Line Items]
Revenues	298	258
Operating segment | O&R
Segment Reporting Information [Line Items]
Revenues	238	215
Operating segment | O&R | Electric
Segment Reporting Information [Line Items]
Revenues	141	140
Operating segment | O&R | Gas
Segment Reporting Information [Line Items]
Revenues	97	75
Other
Segment Reporting Information [Line Items]
Revenues	(2)	(1)
Depreciation and amortization	1	(1)
Operating income/(loss)	1	0
Inter-segment
Segment Reporting Information [Line Items]
Revenues	0	(6)
Inter-segment | Clean Energy Businesses
Segment Reporting Information [Line Items]
Revenues	0	6
Inter-segment | CECONY
Segment Reporting Information [Line Items]
Revenues	(24)	(27)
Inter-segment | CECONY | Electric
Segment Reporting Information [Line Items]
Revenues	5	4
Inter-segment | CECONY | Gas
Segment Reporting Information [Line Items]
Revenues	1	1
Inter-segment | CECONY | Steam
Segment Reporting Information [Line Items]
Revenues	$ 18	$ 22