Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 3,338	$ 3,337	$ 9,123	$ 9,264
Total revenues	3,333	3,365	9,286	9,623
Other
Disaggregation of Revenue [Line Items]
Total revenues	(5)	28	163	359
Clean Energy Businesses | Renewables | Engineering, procurement and construction
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2	3	6	9
CECONY
Disaggregation of Revenue [Line Items]
Total revenues	2,872	2,877	8,072	8,248
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	3,333	3,365
Operating Segments | Electric
Disaggregation of Revenue [Line Items]
Total revenues			9,286	9,623
Operating Segments | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	208	207	523	518
Total revenues	222	247	566	696
Operating Segments | Clean Energy Businesses | Other
Disaggregation of Revenue [Line Items]
Total revenues	14	40	43	178
Operating Segments | Clean Energy Businesses | Renewables
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	194	193	487	465
Total revenues	194	193	487	465
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	14	14	36	53
Total revenues	14	14	36	53
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	14	40	43	178
Operating Segments | Clean Energy Businesses | Other | Other
Disaggregation of Revenue [Line Items]
Total revenues	14	40	43	178
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
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,892	2,899	7,963	8,077
Total revenues	2,872	2,877	8,072	8,248
Operating Segments | CECONY | Other
Disaggregation of Revenue [Line Items]
Total revenues	(20)	(22)	109	171
Operating Segments | CECONY | Electric
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,594	2,582	6,108	6,048
Total revenues	2,562	2,544	6,178	6,174
Operating Segments | CECONY | Electric | Other
Disaggregation of Revenue [Line Items]
Total revenues	(32)	(38)	70	126
Operating Segments | CECONY | Gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	248	263	1,480	1,573
Total revenues	259	275	1,509	1,605
Operating Segments | CECONY | Gas | Other
Disaggregation of Revenue [Line Items]
Total revenues	11	12	29	32
Operating Segments | CECONY | Steam
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	50	54	375	456
Total revenues	51	58	385	469
Operating Segments | CECONY | Steam | Other
Disaggregation of Revenue [Line Items]
Total revenues	1	4	10	13
Operating Segments | O&R
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	237	230	634	666
Total revenues	238	241	647	678
Operating Segments | O&R | Other
Disaggregation of Revenue [Line Items]
Total revenues	1	11	13	12
Operating Segments | O&R | Electric
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	210	205	478	488
Total revenues	208	210	483	493
Operating Segments | O&R | Electric | Other
Disaggregation of Revenue [Line Items]
Total revenues	(2)	5	5	5
Operating Segments | O&R | Gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	27	25	156	178
Total revenues	30	31	164	185
Operating Segments | O&R | Gas | Other
Disaggregation of Revenue [Line Items]
Total revenues	3	6	8	7
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0	0
Total revenues	0	(1)	(2)	(2)
Other | Other
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ (1)	$ (2)	$ (2)