Summary of Significant Accounting Policies - Capitalized Cost of Utility Plant (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Public Utility, Property, Plant and Equipment [Line Items]
General	$ 2,465	$ 2,336
Held for future use	76us-gaap_PlantHeldForFutureUseAmount	73us-gaap_PlantHeldForFutureUseAmount
Construction work in progress	1,031	1,393
NET UTILITY PLANT	29,326	27,795
Electric Generation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Generation	451	452
Electric Transmission [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Transmission	2,956	2,776
Electric Distribution [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Distribution	16,361	15,277
Gas [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Gas	5,006	4,469
Steam [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Steam	1,795	1,790
General [Member]
Public Utility, Property, Plant and Equipment [Line Items]
General	1,650	1,565
CECONY [Member]
Public Utility, Property, Plant and Equipment [Line Items]
General	2,265	2,154
Held for future use	65	62
Construction work in progress	971	1,303
NET UTILITY PLANT	27,585	26,146
CECONY [Member] \| Electric Generation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Generation	451	452
CECONY [Member] \| Electric Transmission [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Transmission	2,744	2,597
CECONY [Member] \| Electric Distribution [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Distribution	15,531	14,496
CECONY [Member] \| Gas [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Gas	4,530	4,013
CECONY [Member] \| Steam [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Steam	1,795	1,790
CECONY [Member] \| General [Member]
Public Utility, Property, Plant and Equipment [Line Items]
General	$ 1,498	$ 1,433

Public Utilities Property Plant And Equipment Steam

No definition available.

Name:	ed_PublicUtilitiesPropertyPlantAndEquipmentSteam
Namespace Prefix:	ed_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Discloses the period end amount of plants held for future use and whether such amount is included in the utility's rate base.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.13(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_PlantHeldForFutureUseAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Period end amount of property, plant and equipment (PPE) related to regulated assets common to business units.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesPropertyPlantAndEquipmentCommon
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Period end amount of construction work in progress in public utility.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Period end amount of property, plant and equipment (PPE) related to utility distribution.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesPropertyPlantAndEquipmentDistribution
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Period end amount of property, plant and equipment (PPE) related to fuels owned by the public utility.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesPropertyPlantAndEquipmentFuel
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Period end amount of property, plant and equipment (PPE) related to generation or processing owned by public utility.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesPropertyPlantAndEquipmentGenerationOrProcessing
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Period end amount of total net PPE.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Period end amount of property, plant and equipment (PPE) related to utility transmission owned by public utility.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesPropertyPlantAndEquipmentTransmission
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_PublicUtilityPropertyPlantAndEquipmentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=ed_CeconyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityAxis=ed_GeneralUtilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityAxis=us-gaap_ElectricDistributionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityAxis=us-gaap_ElectricityGenerationPlantNonNuclearMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityAxis=us-gaap_ElectricTransmissionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityAxis=us-gaap_GasTransmissionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilityAxis=us-gaap_SteamPlantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: