Financial Information by Business Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Total revenues	$ 3,365	$ 3,328	$ 9,623	$ 9,388
Depreciation and amortization	421	360	1,253	1,061
Operating income/(loss)	867	826	2,111	2,007
Clean Energy Businesses
Segment Reporting Information [Line Items]
Depreciation and amortization	53	18	169	55
Operating income/(loss)	100	25	183	59
Con Edison Transmission
Segment Reporting Information [Line Items]
Depreciation and amortization	0	0	1	1
Operating income/(loss)	(1)	(2)	(5)	(5)
CECONY
Segment Reporting Information [Line Items]
Total revenues	2,877	2,899	8,248	8,121
Depreciation and amortization	346	322	1,020	949
Operating income/(loss)	723	764	1,825	1,850
CECONY | Electric
Segment Reporting Information [Line Items]
Depreciation and amortization	266	248	785	732
Operating income/(loss)	803	850	1,374	1,421
CECONY | Gas
Segment Reporting Information [Line Items]
Depreciation and amortization	58	52	168	152
Operating income/(loss)	(24)	(34)	414	369
CECONY | Steam
Segment Reporting Information [Line Items]
Depreciation and amortization	22	22	67	65
Operating income/(loss)	(56)	(52)	37	60
O&R
Segment Reporting Information [Line Items]
Depreciation and amortization	22	19	63	57
Operating income/(loss)	46	42	113	110
O&R | Electric
Segment Reporting Information [Line Items]
Depreciation and amortization	16	14	46	41
Operating income/(loss)	56	52	88	79
O&R | Gas
Segment Reporting Information [Line Items]
Depreciation and amortization	6	5	17	16
Operating income/(loss)	(10)	(10)	25	31
Operating segment
Segment Reporting Information [Line Items]
Total revenues	3,365	3,328	9,623	9,388
Operating segment | Clean Energy Businesses
Segment Reporting Information [Line Items]
Total revenues	247	181	696	573
Operating segment | Con Edison Transmission
Segment Reporting Information [Line Items]
Total revenues	1	1	3	3
Operating segment | CECONY
Segment Reporting Information [Line Items]
Total revenues	2,877	2,899	8,248	8,121
Operating segment | CECONY | Electric
Segment Reporting Information [Line Items]
Total revenues	2,544	2,571	6,174	6,107
Operating segment | CECONY | Gas
Segment Reporting Information [Line Items]
Total revenues	275	264	1,605	1,540
Operating segment | CECONY | Steam
Segment Reporting Information [Line Items]
Total revenues	58	64	469	474
Operating segment | O&R
Segment Reporting Information [Line Items]
Total revenues	241	246	678	691
Operating segment | O&R | Electric
Segment Reporting Information [Line Items]
Total revenues	210	212	493	505
Operating segment | O&R | Gas
Segment Reporting Information [Line Items]
Total revenues	31	34	185	186
Other
Segment Reporting Information [Line Items]
Total revenues	(1)	1	(2)	0
Depreciation and amortization	0	1	0	(1)
Operating income/(loss)	(1)	(3)	(5)	(7)
Inter-segment | CECONY
Segment Reporting Information [Line Items]
Total revenues	(24)	(25)	(71)	(74)
Inter-segment | CECONY | Electric
Segment Reporting Information [Line Items]
Total revenues	4	4	13	12
Inter-segment | CECONY | Gas
Segment Reporting Information [Line Items]
Total revenues	2	2	6	6
Inter-segment | CECONY | Steam
Segment Reporting Information [Line Items]
Total revenues	$ 18	$ 19	$ 52	$ 56