Financial Information by Business Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Total revenues	$ 3,613	$ 3,333	$ 10,261	$ 9,286
Depreciation and amortization	512	482	1,511	1,428
Operating income/(loss)	850	860	2,129	2,147
Subsidiaries
Segment Reporting Information [Line Items]
Total revenues	3,092	2,872	8,784	8,072
Depreciation and amortization	429	401	1,267	1,187
Operating income/(loss)	728	722	1,836	1,854
Clean Energy Businesses
Segment Reporting Information [Line Items]
Depreciation and amortization	58	58	172	173
Operating income/(loss)	79	92	196	188
Con Edison Transmission
Segment Reporting Information [Line Items]
Depreciation and amortization	0	0	1	1
Operating income/(loss)	(2)	(2)	(7)	(6)
Electric
Segment Reporting Information [Line Items]
Depreciation and amortization			1,511	1,428
Operating income/(loss)			2,129	2,147
CECONY | Subsidiaries
Segment Reporting Information [Line Items]
Depreciation and amortization	429	401	1,267	1,187
Operating income/(loss)	728	722	1,836	1,854
CECONY | Electric | Subsidiaries
Segment Reporting Information [Line Items]
Depreciation and amortization	324	305	959	904
Operating income/(loss)	834	813	1,337	1,413
CECONY | Gas | Subsidiaries
Segment Reporting Information [Line Items]
Depreciation and amortization	82	74	239	216
Operating income/(loss)	(48)	(34)	490	440
CECONY | Steam | Subsidiaries
Segment Reporting Information [Line Items]
Depreciation and amortization	23	22	69	67
Operating income/(loss)	(58)	(57)	9	1
O&R | Subsidiaries
Segment Reporting Information [Line Items]
Depreciation and amortization	24	23	71	67
Operating income/(loss)	47	49	108	114
O&R | Electric | Subsidiaries
Segment Reporting Information [Line Items]
Depreciation and amortization	18	17	52	48
Operating income/(loss)	55	58	78	86
O&R | Gas | Subsidiaries
Segment Reporting Information [Line Items]
Depreciation and amortization	6	6	19	19
Operating income/(loss)	(8)	(9)	30	28
Operating segment
Segment Reporting Information [Line Items]
Total revenues	3,613	3,333
Operating segment | Clean Energy Businesses
Segment Reporting Information [Line Items]
Total revenues	264	222	779	566
Operating segment | Con Edison Transmission
Segment Reporting Information [Line Items]
Total revenues	1	1	3	3
Operating segment | Electric
Segment Reporting Information [Line Items]
Total revenues			10,261	9,286
Operating segment | CECONY | Subsidiaries
Segment Reporting Information [Line Items]
Total revenues	3,092	2,872	8,784	8,072
Operating segment | CECONY | Electric | Subsidiaries
Segment Reporting Information [Line Items]
Total revenues	2,730	2,562	6,661	6,178
Operating segment | CECONY | Gas | Subsidiaries
Segment Reporting Information [Line Items]
Total revenues	307	259	1,730	1,509
Operating segment | CECONY | Steam | Subsidiaries
Segment Reporting Information [Line Items]
Total revenues	55	51	393	385
Operating segment | O&R | Subsidiaries
Segment Reporting Information [Line Items]
Total revenues	257	238	699	647
Operating segment | O&R | Electric | Subsidiaries
Segment Reporting Information [Line Items]
Total revenues	223	208	522	483
Operating segment | O&R | Gas | Subsidiaries
Segment Reporting Information [Line Items]
Total revenues	34	30	177	164
Other
Segment Reporting Information [Line Items]
Total revenues	(1)	0	(4)	(2)
Depreciation and amortization	1	0	0	0
Operating income/(loss)	(2)	(1)	(4)	(3)
Other | Con Edison Transmission
Segment Reporting Information [Line Items]
Total revenues			3
Inter-segment | Electric
Segment Reporting Information [Line Items]
Total revenues	0	0	0	0
Inter-segment | CECONY | Subsidiaries
Segment Reporting Information [Line Items]
Total revenues	(25)	(24)	(75)	(74)
Inter-segment | CECONY | Electric | Subsidiaries
Segment Reporting Information [Line Items]
Total revenues	5	4	14	13
Inter-segment | CECONY | Gas | Subsidiaries
Segment Reporting Information [Line Items]
Total revenues	2	2	6	5
Inter-segment | CECONY | Steam | Subsidiaries
Segment Reporting Information [Line Items]
Total revenues	$ 18	$ 18	$ 55	$ 56