Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 3,659	$ 3,338	$ 10,212	$ 9,123
Total revenues	3,613	3,333	10,261	9,286
Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	3,092	2,872	8,784	8,072
Other
Disaggregation of Revenue [Line Items]
Total revenues	(46)	(5)	49	163
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	3,613	3,333
Operating Segments | Electric
Disaggregation of Revenue [Line Items]
Total revenues			10,261	9,286
Operating Segments | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	264	208	713	523
Total revenues	264	222	779	566
Operating Segments | Clean Energy Businesses | Other
Disaggregation of Revenue [Line Items]
Total revenues	0	14	66	43
Operating Segments | Clean Energy Businesses | Renewables
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	199	194	545	487
Total revenues	199	194	545	487
Operating Segments | Clean Energy Businesses | Renewables | Other
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Clean Energy Businesses | Energy services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	65	14	168	36
Total revenues	65	14	168	36
Operating Segments | Clean Energy Businesses | Energy services | Other
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | Clean Energy Businesses | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0	0
Total revenues	0	14	66	43
Operating Segments | Clean Energy Businesses | Other | Other
Disaggregation of Revenue [Line Items]
Total revenues	0	14	66	43
Operating Segments | Con Edison Transmission
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1	1	3	3
Total revenues	1	1	3	3
Operating Segments | Con Edison Transmission | Other
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Operating Segments | CECONY | Subsidiaries
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,133	2,892	8,777	7,963
Total revenues	3,092	2,872	8,784	8,072
Operating Segments | CECONY | Other | Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	(41)	(20)	7	109
Operating Segments | CECONY | Electric | Subsidiaries
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,776	2,594	6,695	6,108
Total revenues	2,730	2,562	6,661	6,178
Operating Segments | CECONY | Electric | Other | Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	(46)	(32)	(34)	70
Operating Segments | CECONY | Gas | Subsidiaries
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	305	248	1,699	1,480
Total revenues	307	259	1,730	1,509
Operating Segments | CECONY | Gas | Other | Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	2	11	31	29
Operating Segments | CECONY | Steam | Subsidiaries
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	52	50	383	375
Total revenues	55	51	393	385
Operating Segments | CECONY | Steam | Other | Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	3	1	10	10
Operating Segments | O&R | Subsidiaries
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	261	237	719	634
Total revenues	257	238	699	647
Operating Segments | O&R | Other | Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	(4)	1	(20)	13
Operating Segments | O&R | Electric | Subsidiaries
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	229	210	535	478
Total revenues	223	208	522	483
Operating Segments | O&R | Electric | Other | Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	(6)	(2)	(13)	5
Operating Segments | O&R | Gas | Subsidiaries
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	32	27	184	156
Total revenues	34	30	177	164
Operating Segments | O&R | Gas | Other | Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	2	3	(7)	8
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0	0
Total revenues	(1)	0	(4)	(2)
Other | Other
Disaggregation of Revenue [Line Items]
Total revenues	$ (1)	$ 0	(4)	$ (2)
Other | Con Edison Transmission
Disaggregation of Revenue [Line Items]
Total revenues			$ 3