Financial Information by Business Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 3,328	$ 3,211	$ 9,388	$ 9,072
Depreciation and amortization	360	337	1,061	998
Operating income/(loss)	826	914	2,007	2,189
Clean Energy Businesses
Segment Reporting Information [Line Items]
Depreciation and amortization	18	19	55	54
Operating income/(loss)	25	29	59	63
Con Edison Transmission
Segment Reporting Information [Line Items]
Depreciation and amortization			1	0
Operating income/(loss)	(2)	(2)	(5)	(6)
CECONY
Segment Reporting Information [Line Items]
Total revenues	2,899	2,799	8,121	7,948
Depreciation and amortization	322	300	949	891
Operating income/(loss)	764	836	1,850	1,999
CECONY | Electric
Segment Reporting Information [Line Items]
Depreciation and amortization	248	232	732	690
Operating income/(loss)	850	883	1,421	1,561
CECONY | Gas
Segment Reporting Information [Line Items]
Depreciation and amortization	52	47	152	137
Operating income/(loss)	(34)	(6)	369	379
CECONY | Steam
Segment Reporting Information [Line Items]
Depreciation and amortization	22	21	65	64
Operating income/(loss)	(52)	(41)	60	59
O&R
Segment Reporting Information [Line Items]
Depreciation and amortization	19	18	57	53
Operating income/(loss)	42	50	110	131
O&R | Electric
Segment Reporting Information [Line Items]
Depreciation and amortization	14	13	41	38
Operating income/(loss)	52	60	79	94
O&R | Gas
Segment Reporting Information [Line Items]
Depreciation and amortization	5	5	16	15
Operating income/(loss)	(10)	(10)	31	37
Operating segment
Segment Reporting Information [Line Items]
Total revenues	3,328	3,211	9,388	9,072
Operating segment | Clean Energy Businesses
Segment Reporting Information [Line Items]
Total revenues	181	177	573	460
Operating segment | Con Edison Transmission
Segment Reporting Information [Line Items]
Total revenues	1	1	3	1
Operating segment | CECONY
Segment Reporting Information [Line Items]
Total revenues	2,899	2,799	8,121	7,948
Operating segment | CECONY | Electric
Segment Reporting Information [Line Items]
Total revenues	2,571	2,469	6,107	6,079
Operating segment | CECONY | Gas
Segment Reporting Information [Line Items]
Total revenues	264	268	1,540	1,421
Operating segment | CECONY | Steam
Segment Reporting Information [Line Items]
Total revenues	64	62	474	448
Operating segment | O&R
Segment Reporting Information [Line Items]
Total revenues	246	234	691	667
Operating segment | O&R | Electric
Segment Reporting Information [Line Items]
Total revenues	212	206	505	495
Operating segment | O&R | Gas
Segment Reporting Information [Line Items]
Total revenues	34	28	186	172
Other
Segment Reporting Information [Line Items]
Total revenues	1	0	0	(4)
Depreciation and amortization	1	0	(1)	0
Operating income/(loss)	(3)	1	(7)	2
Inter-segment | CECONY
Segment Reporting Information [Line Items]
Total revenues	(25)	(25)	(74)	(72)
Inter-segment | CECONY | Electric
Segment Reporting Information [Line Items]
Total revenues	4	4	12	12
Inter-segment | CECONY | Gas
Segment Reporting Information [Line Items]
Total revenues	2	2	6	5
Inter-segment | CECONY | Steam
Segment Reporting Information [Line Items]
Total revenues	$ 19	$ 19	$ 56	$ 55