Derivative Instruments and Hedging Activities - Hedged Volume of Derivative Transactions (Details)	Jun. 30, 2019 MW gal MMBTU MWh
Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	32,178,387
Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	19,324
Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	202,435,409
Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	7,728,000
CECONY | Electric Energy
Derivatives, Fair Value [Line Items]
Notional amount | MWh	29,476,875
CECONY | Capacity
Derivatives, Fair Value [Line Items]
Notional amount | MW	8,550
CECONY | Natural Gas
Derivatives, Fair Value [Line Items]
Notional amount | MMBTU	187,910,000
CECONY | Refined Fuels
Derivatives, Fair Value [Line Items]
Notional amount | gal	7,728,000