Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 12,026	$ 12,144	$ 11,928
Revenues	12,246	12,574	12,337	$ 12,033
Other
Disaggregation of Revenue [Line Items]
Revenues	220	430	409
Clean Energy Businesses | Renewables [Member] | Engineering, procurement and construction
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8	14	103
CECONY
Disaggregation of Revenue [Line Items]
Revenues	10,647	10,821	10,680
Operating Segments | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	661	646	424
Revenues	736	857	763
Operating Segments | Clean Energy Businesses | Other
Disaggregation of Revenue [Line Items]
Revenues	75	211	339
Operating Segments | Clean Energy Businesses | Renewables [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	609	575	329
Revenues	609	575	329
Operating Segments | Clean Energy Businesses | Renewables [Member] | Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Operating Segments | Clean Energy Businesses | Energy Service [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	52	71	95
Revenues	52	71	95
Operating Segments | Clean Energy Businesses | Energy Service [Member] | Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Operating Segments | Clean Energy Businesses | Other Services [Member]
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Revenues	75	211	339
Operating Segments | Clean Energy Businesses | Other Services [Member] | Other
Disaggregation of Revenue [Line Items]
Revenues	75	211	339
Operating Segments | Con Edison Transmission
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	4	4	4
Revenues	4	4	4
Operating Segments | Con Edison Transmission | Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0
Operating Segments | CECONY
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	10,518	10,620	10,597
Revenues	10,647	10,821	10,680
Operating Segments | CECONY | Other
Disaggregation of Revenue [Line Items]
Revenues	129	201	83
Operating Segments | CECONY | Electric
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8,026	7,913	7,920
Revenues	8,103	8,062	7,971
Operating Segments | CECONY | Electric | Other
Disaggregation of Revenue [Line Items]
Revenues	77	149	51
Operating Segments | CECONY | Gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,998	2,097	2,052
Revenues	2,036	2,132	2,078
Operating Segments | CECONY | Gas | Other
Disaggregation of Revenue [Line Items]
Revenues	38	35	26
Operating Segments | CECONY | Steam
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	494	610	625
Revenues	508	627	631
Operating Segments | CECONY | Steam | Other
Disaggregation of Revenue [Line Items]
Revenues	14	17	6
Operating Segments | O&R
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	843	874	903
Revenues	862	893	891
Operating Segments | O&R | Other
Disaggregation of Revenue [Line Items]
Revenues	19	19	(12)
Operating Segments | O&R | Electric
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	619	627	647
Revenues	629	634	642
Operating Segments | O&R | Electric | Other
Disaggregation of Revenue [Line Items]
Revenues	10	7	(5)
Operating Segments | O&R | Gas
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	224	247	256
Revenues	233	259	249
Operating Segments | O&R | Gas | Other
Disaggregation of Revenue [Line Items]
Revenues	9	12	(7)
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0	0	0
Revenues	(3)	(1)	(1)
Other | Other
Disaggregation of Revenue [Line Items]
Revenues	(3)	(1)	(1)
Other | O&R
Disaggregation of Revenue [Line Items]
Revenues	$ 0	$ 0	$ 0