Financial Information by Business Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 2,696	$ 2,633	$ 6,060	$ 5,861
Depreciation and amortization	354	332	702	662
Operating income/(loss)	426	464	1,180	1,275
Clean Energy Businesses
Segment Reporting Information [Line Items]
Depreciation and amortization	19	18	38	36
Operating income/(loss)	24	18	33	34
Con Edison Transmission
Segment Reporting Information [Line Items]
Operating income/(loss)	(1)	(2)	(3)	(5)
CECONY
Segment Reporting Information [Line Items]
Total revenues	2,338	2,293	5,222	5,149
Depreciation and amortization	316	296	626	591
Operating income/(loss)	382	423	1,087	1,163
CECONY | Electric
Segment Reporting Information [Line Items]
Depreciation and amortization	243	229	483	458
Operating income/(loss)	318	358	571	678
CECONY | Gas
Segment Reporting Information [Line Items]
Depreciation and amortization	51	45	100	90
Operating income/(loss)	82	89	404	385
CECONY | Steam
Segment Reporting Information [Line Items]
Depreciation and amortization	22	22	43	43
Operating income/(loss)	(18)	(24)	112	100
O&R
Segment Reporting Information [Line Items]
Depreciation and amortization	19	17	38	35
Operating income/(loss)	23	24	68	81
O&R | Electric
Segment Reporting Information [Line Items]
Depreciation and amortization	14	13	28	25
Operating income/(loss)	18	18	26	35
O&R | Gas
Segment Reporting Information [Line Items]
Depreciation and amortization	5	4	10	10
Operating income/(loss)	5	6	42	46
Operating segment
Segment Reporting Information [Line Items]
Total revenues	2,696	2,633	6,060	5,861
Operating segment | Clean Energy Businesses
Segment Reporting Information [Line Items]
Total revenues	158	146	391	283
Operating segment | Con Edison Transmission
Segment Reporting Information [Line Items]
Total revenues	1	0	2	0
Operating segment | CECONY
Segment Reporting Information [Line Items]
Total revenues	2,338	2,293	5,222	5,149
Operating segment | CECONY | Electric
Segment Reporting Information [Line Items]
Total revenues	1,807	1,817	3,536	3,610
Operating segment | CECONY | Gas
Segment Reporting Information [Line Items]
Total revenues	435	388	1,276	1,153
Operating segment | CECONY | Steam
Segment Reporting Information [Line Items]
Total revenues	96	88	410	386
Operating segment | O&R
Segment Reporting Information [Line Items]
Total revenues	198	195	445	433
Operating segment | O&R | Electric
Segment Reporting Information [Line Items]
Total revenues	144	148	293	289
Operating segment | O&R | Gas
Segment Reporting Information [Line Items]
Total revenues	54	47	152	144
Other
Segment Reporting Information [Line Items]
Total revenues	1	(1)	0	(4)
Depreciation and amortization	0	1	0	0
Operating income/(loss)	(2)	1	(5)	2
Inter-segment | CECONY
Segment Reporting Information [Line Items]
Total revenues	(24)	(24)	(49)	(48)
Inter-segment | CECONY | Electric
Segment Reporting Information [Line Items]
Total revenues	4	4	8	8
Inter-segment | CECONY | Gas
Segment Reporting Information [Line Items]
Total revenues	2	2	4	3
Inter-segment | CECONY | Steam
Segment Reporting Information [Line Items]
Total revenues	$ 18	$ 18	$ 37	$ 37