Derivative Instruments and Hedging Activities - Hedged Volume of Derivative Transactions (Details)	Mar. 31, 2020 MW gal MWh MMBTU
Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	21,682,575
Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	26,614
Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	260,204,579
Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	10,752,000
CECONY | Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	19,582,075
CECONY | Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	21,900
CECONY | Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	241,100,000
CECONY | Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	10,752,000