Financial Information by Business Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 12,246	$ 12,574	$ 12,337	$ 12,033
Depreciation and amortization	1,920	1,684	1,438
Operating income	2,654	2,676	2,664
Other Income (deductions)	(401)	51	(62)
Interest charges	1,019	991	819
Income taxes on operating income	193	300	406
Total assets	62,895	58,079	53,920
Capital expenditures	4,085	3,676	5,249
Income tax expense (benefit) on non-operating income	(103)	(4)	(5)
Parent Company
Segment Reporting Information [Line Items]
Total assets	21,499	20,638
CECONY
Segment Reporting Information [Line Items]
Revenues	10,647	10,821	10,680
Depreciation and amortization	1,598	1,373	1,276
Operating income	2,310	2,348	2,354
Other Income (deductions)	(171)	(35)	(143)
Total assets	50,967	46,557
Income tax expense (benefit) on non-operating income	(3)	(7)	(2)
Operating segment | Clean Energy Businesses
Segment Reporting Information [Line Items]
Revenues	736	857	763
Depreciation and amortization	231	226	85
Operating income	215	202	194
Other Income (deductions)	4	5	33
Interest charges	196	186	63
Income taxes on operating income	(43)	(58)	19
Total assets	6,848	6,528	5,821
Capital expenditures	616	248	1,791
Operating segment | Con Edison Transmission
Segment Reporting Information [Line Items]
Revenues	4	4	4
Depreciation and amortization	1	1	1
Operating income	(8)	(6)	(7)
Other Income (deductions)	(215)	104	91
Interest charges	18	25	20
Income taxes on operating income	0	1	(1)
Total assets	1,348	1,618	1,425
Capital expenditures	3	205	248
Operating segment | CECONY
Segment Reporting Information [Line Items]
Revenues	10,647	10,821	10,680
Depreciation and amortization	1,598	1,373	1,276
Operating income	2,310	2,348	2,354
Other Income (deductions)	(171)	(35)	(143)
Interest charges	739	728	689
Income taxes on operating income	218	342	328
Total assets	50,967	46,557	43,108
Capital expenditures	3,246	3,020	3,005
Operating segment | CECONY | Electric
Segment Reporting Information [Line Items]
Revenues	8,103	8,062	7,971
Depreciation and amortization	1,214	1,053	984
Operating income	1,731	1,758	1,799
Other Income (deductions)	(134)	(28)	(110)
Interest charges	535	539	519
Income taxes on operating income	130	239	233
Total assets	35,673	32,988	31,012
Capital expenditures	2,080	1,851	1,861
Operating segment | CECONY | Gas
Segment Reporting Information [Line Items]
Revenues	2,036	2,132	2,078
Depreciation and amortization	294	231	205
Operating income	574	528	478
Other Income (deductions)	(25)	(4)	(23)
Interest charges	164	147	131
Income taxes on operating income	102	99	87
Total assets	12,678	11,090	9,710
Capital expenditures	1,044	1,078	1,050
Operating segment | CECONY | Steam
Segment Reporting Information [Line Items]
Revenues	508	627	631
Depreciation and amortization	90	89	87
Operating income	5	62	77
Other Income (deductions)	(12)	(3)	(10)
Interest charges	40	42	39
Income taxes on operating income	(14)	4	8
Total assets	2,616	2,479	2,386
Capital expenditures	122	91	94
Operating segment | O&R
Segment Reporting Information [Line Items]
Revenues	862	893	891
Depreciation and amortization	90	84	77
Operating income	147	139	132
Other Income (deductions)	(14)	(11)	(19)
Interest charges	41	41	39
Income taxes on operating income	21	21	21
Total assets	3,247	3,006	2,892
Capital expenditures	220	203	205
Operating segment | O&R | Electric
Segment Reporting Information [Line Items]
Revenues	629	634	642
Depreciation and amortization	65	60	56
Operating income	99	98	93
Other Income (deductions)	(10)	(7)	(14)
Interest charges	26	27	25
Income taxes on operating income	13	15	14
Total assets	2,097	2,130	2,036
Capital expenditures	159	142	138
Operating segment | O&R | Gas
Segment Reporting Information [Line Items]
Revenues	233	259	249
Depreciation and amortization	25	24	21
Operating income	48	41	39
Other Income (deductions)	(4)	(4)	(5)
Interest charges	15	14	14
Income taxes on operating income	8	6	7
Total assets	1,150	876	856
Capital expenditures	61	61	67
Other
Segment Reporting Information [Line Items]
Revenues	(3)	(1)	(1)
Depreciation and amortization	0	0	(1)
Operating income	(10)	(7)	(9)
Other Income (deductions)	(5)	(12)	(24)
Interest charges	25	11	8
Income taxes on operating income	(3)	(6)	39
Total assets	485	370	674
Capital expenditures	0	0	0
Other | O&R
Segment Reporting Information [Line Items]
Revenues	0	0	0
Depreciation and amortization	0	0	0
Operating income	0	0	0
Other Income (deductions)	0	0	0
Interest charges	0	0	0
Income taxes on operating income	0	0	0
Total assets	0	0	0
Capital expenditures	0	0	0
Inter-segment
Segment Reporting Information [Line Items]
Revenues	0	0	0
Inter-segment | Clean Energy Businesses
Segment Reporting Information [Line Items]
Revenues	0	0	0
Inter-segment | CECONY
Segment Reporting Information [Line Items]
Revenues	(99)	(94)	(98)
Inter-segment | CECONY | Electric
Segment Reporting Information [Line Items]
Revenues	18	17	16
Inter-segment | CECONY | Gas
Segment Reporting Information [Line Items]
Revenues	7	7	7
Inter-segment | CECONY | Steam
Segment Reporting Information [Line Items]
Revenues	$ 74	$ 70	$ 75