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Other Material Contingencies - Additional Information (Detail) (USD $)
 1 Months Ended 12 Months Ended
Jul. 31, 2007
Person
Dec. 31, 2014
People
Lawsuits
Dec. 31, 2013
Guarantor Obligations [Line Items]      
Number of person died in steam ruptured 1ed_NumberOfPersonsDiedInSteamRuptured    
Number of suits pending against the company   90ed_NumberOfLawsuits  
Estimated accrued liability for suits   $ 50,000,000us-gaap_LossContingencyLossInPeriod  
Insurance receivable for suits   50,000,000us-gaap_InsuranceSettlementsReceivable  
Description of explosion and fire incident   On March 12, 2014, two multi-use five-story tall buildings located on Park Avenue between 116th and 117th Street in Manhattan were destroyed by an explosion and fire. CECONY had delivered gas to the buildings through service lines from a distribution main located below ground on Park Avenue. Eight people died and more than 48 people were injured. Additional buildings were also damaged.  
Number of people died in explosion and fire incident   8ed_NumberOfPeopleDiedInExplosionAndFireIncident  
Number of people injured in explosion and fire incident   48ed_NumberOfPeopleInjuredInExplosionAndFireIncident  
Guarantee obligations maximum exposure   2,547,000,000us-gaap_GuaranteeObligationsMaximumExposure 1,331,000,000us-gaap_GuaranteeObligationsMaximumExposure
Ownership interest, percentage   46.00%us-gaap_MinorityInterestOwnershipPercentageByParent  
Estimated project cost percentage   175.00%ed_PercentageOfEstimatedCostsOnProjects  
Manhattan Explosion and Fire [Member]      
Guarantor Obligations [Line Items]      
Number of suits pending against the company   30ed_NumberOfLawsuits
/ us-gaap_LitigationCaseAxis
= ed_ManhattanExplosionAndFireMember		  
Other [Member]      
Guarantor Obligations [Line Items]      
Guarantee obligations maximum exposure   30,000,000us-gaap_GuaranteeObligationsMaximumExposure
/ us-gaap_GuaranteeObligationsByNatureAxis
= ed_FinancialAndPerformanceGuaranteeOtherMember		  
Electric provider obligation to Public Utility Commission of Texas   5,000,000ed_ElectricObligationToStateUtility
/ us-gaap_GuaranteeObligationsByNatureAxis
= ed_FinancialAndPerformanceGuaranteeOtherMember		  
Indemnity agreements amount   25,000,000ed_MaximumAmountReimbursableUnderIndemnityAgreement
/ us-gaap_GuaranteeObligationsByNatureAxis
= ed_FinancialAndPerformanceGuaranteeOtherMember		  
Con Edison Development [Member]      
Guarantor Obligations [Line Items]      
Percentage of variable interests   50.00%us-gaap_VariableInterestEntityOwnershipPercentage
/ us-gaap_GuaranteeObligationsByNatureAxis
= ed_ConEdisonDevelopmentMember		  
Number of guaranteed payments   2ed_NumberOfGuaranteedPayments
/ us-gaap_GuaranteeObligationsByNatureAxis
= ed_ConEdisonDevelopmentMember		  
Con Edison Development [Member] | Guarantee One [Member]      
Guarantor Obligations [Line Items]      
Guarantee obligations maximum exposure   63,000,000us-gaap_GuaranteeObligationsMaximumExposure
/ us-gaap_GuaranteeObligationsByNatureAxis
= ed_ConEdisonDevelopmentMember
/ us-gaap_OtherCommitmentsAxis
= ed_GuaranteeOneMember		  
Con Edison Development [Member] | Guarantee Two [Member]      
Guarantor Obligations [Line Items]      
Guarantee obligations maximum exposure   31,000,000us-gaap_GuaranteeObligationsMaximumExposure
/ us-gaap_GuaranteeObligationsByNatureAxis
= ed_ConEdisonDevelopmentMember
/ us-gaap_OtherCommitmentsAxis
= ed_GuaranteeTwoMember		  
Construction and Operation of Solar Energy Facilities [Member]      
Guarantor Obligations [Line Items]      
Guarantees issued   $ 3,000,000ed_ParentalGuaranteesIssued
/ us-gaap_GuaranteeObligationsByNatureAxis
= ed_ConstructionAndOperationOfSolarFacilitiesMember