Derivative Instruments and Hedging Activities - Hedged Volume of Derivative Transactions (Detail)	6 Months Ended
	Jun. 30, 2016 DTH MWh MW gal
Electric Energy Derivative
Derivatives, Fair Value [Line Items]
Electric Energy (MWH) | MWh	31,244,951
Electric Capacity Derivative
Derivatives, Fair Value [Line Items]
Capacity (MW) | MW	23,618
Natural Gas Derivative
Derivatives, Fair Value [Line Items]
Natural Gas (Dt) | DTH	39,700,166
Refined Fuels
Derivatives, Fair Value [Line Items]
Refined fuel (gallons) | gal	3,360,000
CECONY | Electric Energy Derivative
Derivatives, Fair Value [Line Items]
Electric Energy (MWH) | MWh	15,349,625
CECONY | Electric Capacity Derivative
Derivatives, Fair Value [Line Items]
Capacity (MW) | MW	10,200
CECONY | Natural Gas Derivative
Derivatives, Fair Value [Line Items]
Natural Gas (Dt) | DTH	38,830,000
CECONY | Refined Fuels
Derivatives, Fair Value [Line Items]
Refined fuel (gallons) | gal	3,360,000
Discontinued Operations, Held-for-sale | Electric Energy Derivative
Derivatives, Fair Value [Line Items]
Electric Energy (MWH) | MWh	14,519,076
Discontinued Operations, Held-for-sale | Electric Capacity Derivative
Derivatives, Fair Value [Line Items]
Capacity (MW) | MW	10,779
Discontinued Operations, Held-for-sale | Natural Gas Derivative
Derivatives, Fair Value [Line Items]
Natural Gas (Dt) | DTH	887,007