Summary of Significant Accounting Policies and Other Matters - Capitalized Cost of Utility Plant (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Public Utility, Property, Plant and Equipment [Line Items]
General	$ 3,562	$ 3,331
Held for future use	75	76
Construction work in progress	1,937	1,978
NET UTILITY PLANT	39,751	37,580
Electric Generation
Public Utility, Property, Plant and Equipment [Line Items]
Generation	591	593
Electric Transmission
Public Utility, Property, Plant and Equipment [Line Items]
Transmission	3,634	3,333
Electric Distribution
Public Utility, Property, Plant and Equipment [Line Items]
Distribution	20,676	19,750
General
Public Utility, Property, Plant and Equipment [Line Items]
General	43	0
Gas
Public Utility, Property, Plant and Equipment [Line Items]
Gas	8,617	7,714
Steam
Public Utility, Property, Plant and Equipment [Line Items]
Steam	1,813	1,830
General
Public Utility, Property, Plant and Equipment [Line Items]
General	2,365	2,306
CECONY
Public Utility, Property, Plant and Equipment [Line Items]
General	3,271	3,056
Held for future use	67	67
Construction work in progress	1,812	1,850
NET UTILITY PLANT	37,412	35,370
CECONY | Electric Generation
Public Utility, Property, Plant and Equipment [Line Items]
Generation	591	592
CECONY | Electric Transmission
Public Utility, Property, Plant and Equipment [Line Items]
Transmission	3,380	3,106
CECONY | Electric Distribution
Public Utility, Property, Plant and Equipment [Line Items]
Distribution	19,602	18,716
CECONY | General
Public Utility, Property, Plant and Equipment [Line Items]
General	43	0
CECONY | Gas
Public Utility, Property, Plant and Equipment [Line Items]
Gas	7,961	7,107
CECONY | Steam
Public Utility, Property, Plant and Equipment [Line Items]
Steam	1,813	1,830
CECONY | General
Public Utility, Property, Plant and Equipment [Line Items]
General	$ 2,143	$ 2,102