Derivative Instruments and Hedging Activities - Hedged Volume of Derivative Transactions (Details)	Sep. 30, 2020 MWh MMBTU MW gal
Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	30,693,295
Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	41,993
Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	304,371,409
Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	8,736,000
CECONY | Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	28,628,075
CECONY | Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	32,400
CECONY | Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	288,330,000
CECONY | Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	8,736,000