Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 3,602	$ 3,157
Total revenues	3,677	3,234
Other
Disaggregation of Revenue [Line Items]
Total revenues	75	77
CECONY
Disaggregation of Revenue [Line Items]
Total revenues	3,205	2,854
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	3,677	3,234
Operating Segments | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	176	125
Total revenues	224	146
Operating Segments | Clean Energy Businesses | Other
Disaggregation of Revenue [Line Items]
Total revenues	48	21
Operating Segments | Clean Energy Businesses | Renewables
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	154	114
Total revenues	154	114
Operating Segments | Clean Energy Businesses | Renewables | Other
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Clean Energy Businesses | Energy services
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	22	11
Total revenues	22	11
Operating Segments | Clean Energy Businesses | Energy services | Other
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | Clean Energy Businesses | Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Total revenues	48	21
Operating Segments | Clean Energy Businesses | Other | Other
Disaggregation of Revenue [Line Items]
Total revenues	48	21
Operating Segments | Con Edison Transmission
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1	1
Total revenues	1	1
Operating Segments | Con Edison Transmission | Other
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Operating Segments | CECONY
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,173	2,810
Total revenues	3,205	2,854
Operating Segments | CECONY | Other
Disaggregation of Revenue [Line Items]
Total revenues	32	44
Operating Segments | CECONY | Electric
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,966	1,732
Total revenues	1,968	1,770
Operating Segments | CECONY | Electric | Other
Disaggregation of Revenue [Line Items]
Total revenues	2	38
Operating Segments | CECONY | Gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	946	833
Total revenues	973	834
Operating Segments | CECONY | Gas | Other
Disaggregation of Revenue [Line Items]
Total revenues	27	1
Operating Segments | CECONY | Steam
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	261	245
Total revenues	264	250
Operating Segments | CECONY | Steam | Other
Disaggregation of Revenue [Line Items]
Total revenues	3	5
Operating Segments | O&R
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	252	221
Total revenues	248	233
Operating Segments | O&R | Other
Disaggregation of Revenue [Line Items]
Total revenues	(4)	12
Operating Segments | O&R | Electric
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	144	128
Total revenues	145	136
Operating Segments | O&R | Electric | Other
Disaggregation of Revenue [Line Items]
Total revenues	1	8
Operating Segments | O&R | Gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	108	93
Total revenues	103	97
Operating Segments | O&R | Gas | Other
Disaggregation of Revenue [Line Items]
Total revenues	(5)	4
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Total revenues	(1)	0
Other | Other
Disaggregation of Revenue [Line Items]
Total revenues	$ (1)	$ 0