Derivative Instruments and Hedging Activities - Hedged Volume of Derivative Transactions (Details)	Dec. 31, 2020 gal MMBTU MWh MW
Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	28,102,230
Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	47,258
Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	286,819,910
Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	7,728,000
CECONY | Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	26,193,800
CECONY | Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	35,400
CECONY | Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	267,380,000
CECONY | Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	7,728,000