Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 3,157	$ 3,328
Total revenues	3,234	3,514
Other
Disaggregation of Revenue [Line Items]
Total revenues	77	186
Clean Energy Businesses | Renewables | Engineering, procurement and construction
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3	2
CECONY
Disaggregation of Revenue [Line Items]
Total revenues	2,854	3,039
Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	3,234	3,514
Operating Segments | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	125	129
Total revenues	146	217
Operating Segments | Clean Energy Businesses | Other
Disaggregation of Revenue [Line Items]
Total revenues	21	88
Operating Segments | Clean Energy Businesses | Renewables
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	114	106
Total revenues	114	106
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	11	23
Total revenues	11	23
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	21	88
Operating Segments | Clean Energy Businesses | Other | Other
Disaggregation of Revenue [Line Items]
Total revenues	21	88
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	2,810	2,941
Total revenues	2,854	3,039
Operating Segments | CECONY | Other
Disaggregation of Revenue [Line Items]
Total revenues	44	98
Operating Segments | CECONY | Electric
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,732	1,714
Total revenues	1,770	1,797
Operating Segments | CECONY | Electric | Other
Disaggregation of Revenue [Line Items]
Total revenues	38	83
Operating Segments | CECONY | Gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	833	910
Total revenues	834	921
Operating Segments | CECONY | Gas | Other
Disaggregation of Revenue [Line Items]
Total revenues	1	11
Operating Segments | CECONY | Steam
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	245	317
Total revenues	250	321
Operating Segments | CECONY | Steam | Other
Disaggregation of Revenue [Line Items]
Total revenues	5	4
Operating Segments | O&R
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	221	257
Total revenues	233	258
Operating Segments | O&R | Other
Disaggregation of Revenue [Line Items]
Total revenues	12	1
Operating Segments | O&R | Electric
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	128	143
Total revenues	136	145
Operating Segments | O&R | Electric | Other
Disaggregation of Revenue [Line Items]
Total revenues	8	2
Operating Segments | O&R | Gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	93	114
Total revenues	97	113
Operating Segments | O&R | Gas | Other
Disaggregation of Revenue [Line Items]
Total revenues	4	(1)
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0
Total revenues	0	(1)
Other | Other
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ (1)