Financial Information by Business Segment (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Total revenues	$ 3,677	$ 3,234
Depreciation and amortization	497	470
Operating income/(loss)	860	808
Clean Energy Businesses
Segment Reporting Information [Line Items]
Depreciation and amortization	58	57
Operating income/(loss)	28	14
Con Edison Transmission
Segment Reporting Information [Line Items]
Depreciation and amortization	0	1
Operating income/(loss)	(3)	(2)
CECONY
Segment Reporting Information [Line Items]
Total revenues	3,205	2,854
Depreciation and amortization	415	390
Operating income/(loss)	786	742
CECONY | Electric
Segment Reporting Information [Line Items]
Depreciation and amortization	315	297
Operating income/(loss)	247	282
CECONY | Gas
Segment Reporting Information [Line Items]
Depreciation and amortization	77	71
Operating income/(loss)	439	369
CECONY | Steam
Segment Reporting Information [Line Items]
Depreciation and amortization	23	22
Operating income/(loss)	100	91
O&R
Segment Reporting Information [Line Items]
Depreciation and amortization	24	22
Operating income/(loss)	49	55
O&R | Electric
Segment Reporting Information [Line Items]
Depreciation and amortization	17	16
Operating income/(loss)	9	14
O&R | Gas
Segment Reporting Information [Line Items]
Depreciation and amortization	7	6
Operating income/(loss)	40	41
Operating segment
Segment Reporting Information [Line Items]
Total revenues	3,677	3,234
Operating segment | Clean Energy Businesses
Segment Reporting Information [Line Items]
Total revenues	224	146
Operating segment | Con Edison Transmission
Segment Reporting Information [Line Items]
Total revenues	1	1
Operating segment | CECONY
Segment Reporting Information [Line Items]
Total revenues	3,205	2,854
Operating segment | CECONY | Electric
Segment Reporting Information [Line Items]
Total revenues	1,968	1,770
Operating segment | CECONY | Gas
Segment Reporting Information [Line Items]
Total revenues	973	834
Operating segment | CECONY | Steam
Segment Reporting Information [Line Items]
Total revenues	264	250
Operating segment | O&R
Segment Reporting Information [Line Items]
Total revenues	248	233
Operating segment | O&R | Electric
Segment Reporting Information [Line Items]
Total revenues	145	136
Operating segment | O&R | Gas
Segment Reporting Information [Line Items]
Total revenues	103	97
Other
Segment Reporting Information [Line Items]
Total revenues	(1)	0
Depreciation and amortization	0	0
Operating income/(loss)	0	(1)
Inter-segment | CECONY
Segment Reporting Information [Line Items]
Total revenues	(25)	(25)
Inter-segment | CECONY | Electric
Segment Reporting Information [Line Items]
Total revenues	4	4
Inter-segment | CECONY | Gas
Segment Reporting Information [Line Items]
Total revenues	2	2
Inter-segment | CECONY | Steam
Segment Reporting Information [Line Items]
Total revenues	$ 19	$ 19