Summary of Significant Accounting Policies and Other Matters - Disaggregation of Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 11,928
Total revenues	12,337	$ 12,033	$ 12,075
CECONY
Disaggregation of Revenue [Line Items]
Total revenues	10,680	10,468	10,165
Operating segment | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	424
Total revenues	763	694	1,091
Operating segment | Con Edison Transmission
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	4
Total revenues	4	2	0
Operating segment | CECONY
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	10,597
Total revenues	10,680	10,468	10,165
Operating segment | O&R
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	903
Total revenues	891	874	821
Operating segment | Electric | CECONY
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	7,920
Total revenues	7,971	7,972	8,106
Operating segment | Electric | O&R
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	647
Total revenues	642	642	637
Operating segment | Gas | CECONY
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,052
Total revenues	2,078	1,901	1,508
Operating segment | Gas | O&R
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	256
Total revenues	249	232	184
Operating segment | Steam | CECONY
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	625
Total revenues	631	595	551
Operating segment | Renewables | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	329
Total revenues	329
Operating segment | Energy services | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	95
Total revenues	95
Operating segment | Other | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0
Total revenues	339
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0
Total revenues	(1)	(5)	(2)
Other | O&R
Disaggregation of Revenue [Line Items]
Total revenues	0	$ 0	$ 0
Other
Disaggregation of Revenue [Line Items]
Total revenues	409
Other | Operating segment | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Total revenues	339
Other | Operating segment | Con Edison Transmission
Disaggregation of Revenue [Line Items]
Total revenues	0
Other | Operating segment | CECONY
Disaggregation of Revenue [Line Items]
Total revenues	83
Other | Operating segment | O&R
Disaggregation of Revenue [Line Items]
Total revenues	(12)
Other | Operating segment | Electric | CECONY
Disaggregation of Revenue [Line Items]
Total revenues	51
Other | Operating segment | Electric | O&R
Disaggregation of Revenue [Line Items]
Total revenues	(5)
Other | Operating segment | Gas | CECONY
Disaggregation of Revenue [Line Items]
Total revenues	26
Other | Operating segment | Gas | O&R
Disaggregation of Revenue [Line Items]
Total revenues	(7)
Other | Operating segment | Steam | CECONY
Disaggregation of Revenue [Line Items]
Total revenues	6
Other | Operating segment | Renewables | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Total revenues	0
Other | Operating segment | Energy services | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Total revenues	0
Other | Operating segment | Other | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Total revenues	339
Other | Other
Disaggregation of Revenue [Line Items]
Total revenues	(1)
Engineering, procurement and construction | Renewables | Clean Energy Businesses
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 103