Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 2,950	$ 2,627	$ 6,552	$ 5,784
Total revenues	2,971	2,719	6,648	5,953
Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	2,486	2,345	5,692	5,200
Other
Disaggregation of Revenue [Line Items]
Total revenues	21	92	96	169
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	2,971	2,719
Operating Segments | Electric
Disaggregation of Revenue [Line Items]
Total revenues			6,648	5,953
Operating Segments | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	273	189	449	314
Total revenues	291	198	515	344
Operating Segments | Clean Energy Businesses | Other
Disaggregation of Revenue [Line Items]
Total revenues	18	9	66	30
Operating Segments | Clean Energy Businesses | Renewables
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	192	178	346	292
Total revenues	192	178	346	292
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	81	11	103	22
Total revenues	81	11	103	22
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	18	9	66	30
Operating Segments | Clean Energy Businesses | Other | Other
Disaggregation of Revenue [Line Items]
Total revenues	18	9	66	30
Operating Segments | Con Edison Transmission
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1	1	2	2
Total revenues	1	1	2	2
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	2,471	2,261	5,644	5,071
Total revenues	2,486	2,345	5,692	5,200
Operating Segments | CECONY | Other | Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	15	84	48	129
Operating Segments | CECONY | Electric | Subsidiaries
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,953	1,781	3,919	3,514
Total revenues	1,963	1,845	3,931	3,616
Operating Segments | CECONY | Electric | Other | Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	10	64	12	102
Operating Segments | CECONY | Gas | Subsidiaries
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	447	399	1,394	1,232
Total revenues	449	416	1,423	1,250
Operating Segments | CECONY | Gas | Other | Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	2	17	29	18
Operating Segments | CECONY | Steam | Subsidiaries
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	71	81	331	325
Total revenues	74	84	338	334
Operating Segments | CECONY | Steam | Other | Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	3	3	7	9
Operating Segments | O&R | Subsidiaries
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	205	176	457	397
Total revenues	194	175	442	408
Operating Segments | O&R | Other | Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	(11)	(1)	(15)	11
Operating Segments | O&R | Electric | Subsidiaries
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	161	139	305	267
Total revenues	153	138	299	274
Operating Segments | O&R | Electric | Other | Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	(8)	(1)	(6)	7
Operating Segments | O&R | Gas | Subsidiaries
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	44	37	152	130
Total revenues	41	37	143	134
Operating Segments | O&R | Gas | Other | Subsidiaries
Disaggregation of Revenue [Line Items]
Total revenues	(3)	0	(9)	4
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0	0
Total revenues	(1)	0	(3)	(1)
Other | Other
Disaggregation of Revenue [Line Items]
Total revenues	$ (1)	$ 0	(3)	$ (1)
Other | Con Edison Transmission
Disaggregation of Revenue [Line Items]
Total revenues			$ 2