Derivative Instruments and Hedging Activities - Hedged Volume of Derivative Transactions (Detail)	3 Months Ended
	Mar. 31, 2016 DTH MWh MW gal
Electric Energy Derivative
Derivatives, Fair Value [Line Items]
Electric Energy (MWH) | MWh	34,331,960
Electric Capacity Derivative
Derivatives, Fair Value [Line Items]
Capacity (MW) | MW	26,658
Natural Gas Derivative
Derivatives, Fair Value [Line Items]
Natural Gas (Dt) | DTH	43,472,324
Refined Fuels
Derivatives, Fair Value [Line Items]
Refined fuel (gallons) | gal	5,376,000
CECONY | Electric Energy Derivative
Derivatives, Fair Value [Line Items]
Electric Energy (MWH) | MWh	17,173,925
CECONY | Electric Capacity Derivative
Derivatives, Fair Value [Line Items]
Capacity (MW) | MW	12,000
CECONY | Natural Gas Derivative
Derivatives, Fair Value [Line Items]
Natural Gas (Dt) | DTH	40,280,000
CECONY | Refined Fuels
Derivatives, Fair Value [Line Items]
Refined fuel (gallons) | gal	5,376,000
Discontinued Operations, Held-for-sale | Electric Energy Derivative
Derivatives, Fair Value [Line Items]
Electric Energy (MWH) | MWh	15,495,945
Discontinued Operations, Held-for-sale | Electric Capacity Derivative
Derivatives, Fair Value [Line Items]
Capacity (MW) | MW	11,817
Discontinued Operations, Held-for-sale | Natural Gas Derivative
Derivatives, Fair Value [Line Items]
Natural Gas (Dt) | DTH	552,073