Financial Information by Business Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ 2,633	$ 2,794	$ 5,861	$ 5,950
Depreciation and amortization	332	302	662	599
Operating income/(loss)	423	515	1,193	1,157
Clean Energy Businesses
Segment Reporting Information [Line Items]
Depreciation and amortization	18	10	36	19
Operating income/(loss)	18	109	34	58
Con Edison Transmission
Segment Reporting Information [Line Items]
Operating income/(loss)	(2)	(1)	(4)	(1)
CECONY
Segment Reporting Information [Line Items]
Revenues	2,293	2,281	5,149	4,913
Depreciation and amortization	296	275	591	547
Operating income/(loss)	387	392	1,091	1,033
CECONY | Electric
Segment Reporting Information [Line Items]
Depreciation and amortization	229	215	458	428
Operating income/(loss)	330	371	622	645
CECONY | Gas
Segment Reporting Information [Line Items]
Depreciation and amortization	45	39	90	78
Operating income/(loss)	83	48	374	301
CECONY | Steam
Segment Reporting Information [Line Items]
Depreciation and amortization	22	21	43	41
Operating income/(loss)	(26)	(27)	95	87
O&R
Segment Reporting Information [Line Items]
Depreciation and amortization	17	17	35	33
Operating income/(loss)	19	13	71	66
O&R | Electric
Segment Reporting Information [Line Items]
Depreciation and amortization	13	13	25	24
Operating income/(loss)	14	14	27	32
O&R | Gas
Segment Reporting Information [Line Items]
Depreciation and amortization	4	4	10	9
Operating income/(loss)	5	(1)	44	34
Operating segment
Segment Reporting Information [Line Items]
Revenues	2,633	2,794	5,861	5,950
Operating segment | Clean Energy Businesses
Segment Reporting Information [Line Items]
Revenues	146	338	283	648
Operating segment | CECONY
Segment Reporting Information [Line Items]
Revenues	2,293	2,281	5,149	4,913
Operating segment | CECONY | Electric
Segment Reporting Information [Line Items]
Revenues	1,817	1,892	3,610	3,665
Operating segment | CECONY | Gas
Segment Reporting Information [Line Items]
Revenues	388	304	1,153	905
Operating segment | CECONY | Steam
Segment Reporting Information [Line Items]
Revenues	88	85	386	343
Operating segment | O&R
Segment Reporting Information [Line Items]
Revenues	195	175	433	390
Operating segment | O&R | Electric
Segment Reporting Information [Line Items]
Revenues	148	144	289	284
Operating segment | O&R | Gas
Segment Reporting Information [Line Items]
Revenues	47	31	144	106
Other
Segment Reporting Information [Line Items]
Revenues	(1)	0	(4)	(1)
Depreciation and amortization	1	0	0	0
Operating income/(loss)	1	2	1	1
Inter-segment
Segment Reporting Information [Line Items]
Revenues	0	(3)	0	(9)
Inter-segment | Clean Energy Businesses
Segment Reporting Information [Line Items]
Revenues	0	3	0	9
Inter-segment | CECONY
Segment Reporting Information [Line Items]
Revenues	(24)	(26)	(48)	(56)
Inter-segment | CECONY | Electric
Segment Reporting Information [Line Items]
Revenues	4	4	8	9
Inter-segment | CECONY | Gas
Segment Reporting Information [Line Items]
Revenues	2	1	3	3
Inter-segment | CECONY | Steam
Segment Reporting Information [Line Items]
Revenues	$ 18	$ 21	$ 37	$ 44