Capitalization - Significant Debt Covenants (Details)	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Long-term debt	$ 22,349,000,000	$ 19,973,000,000
Maximum ratio of consolidated debt to consolidated total capital	0.53
CECONY
Debt Instrument [Line Items]
Long-term debt	$ 16,789,000,000	14,964,000,000
Maximum ratio of consolidated debt to consolidated total capital	0.56
Term Loan
Debt Instrument [Line Items]
Maximum ratio of consolidated debt to consolidated total capital	0.65
Covenant principal balance amount limit	$ 150,000,000
Term Loan | Term Loan Due June 2021
Debt Instrument [Line Items]
Debt instrument, face amount	825,000,000
Long-term debt	675,000,000
Term Loan | CECONY
Debt Instrument [Line Items]
Covenant principal balance amount limit	$ 150,000,000
Notes
Debt Instrument [Line Items]
Maximum ratio of consolidated debt to consolidated total capital	0.675
Covenant principal balance amount limit	$ 100,000,000
Notes | CECONY
Debt Instrument [Line Items]
Covenant principal balance amount limit	100,000,000
Tax-Exempt Debt | CECONY
Debt Instrument [Line Items]
Debt instrument, face amount	450,000,000
Long-term debt	$ 450,000,000	$ 450,000,000
Maximum ratio of consolidated debt to consolidated total capital	0.65