Derivative Instruments and Hedging Activities - Hedged Volume of Derivative Transactions (Details)	Jun. 30, 2020 MW MWh gal MMBTU
Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	33,140,975
Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	39,561
Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	286,817,088
Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	9,744,000
CECONY | Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	30,767,675
CECONY | Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	33,900
CECONY | Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	268,660,000
CECONY | Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	9,744,000