Derivative Instruments and Hedging Activities - Hedged Volume of Derivative Transactions (Details)	Mar. 31, 2021 MMBTU MWh MW gal
Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	24,921,520
Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	47,381
Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	259,569,793
Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	6,720,000
CECONY | Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	22,991,350
CECONY | Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	33,000
CECONY | Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	241,610,000
CECONY | Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	6,720,000