Derivative Instruments and Hedging Activities - Hedged Volume of Derivative Transactions (Details)	Dec. 31, 2019 MW gal MMBTU MWh
Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	24,868,670
Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	28,916
Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	277,827,601
Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	5,712,000
CECONY | Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	22,487,800
CECONY | Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	19,950
CECONY | Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	258,080,000
CECONY | Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	5,712,000