Derivative Instruments and Hedging Activities - Hedged Volume of Derivative Transactions (Details)	Sep. 30, 2019 MW gal MWh MMBTU
Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	27,843,993
Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	25,054
Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	277,395,718
Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	6,720,000
CECONY | Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	25,361,275
CECONY | Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	16,800
CECONY | Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	260,350,000
CECONY | Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	6,720,000