Variable Interest Entities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014
Variable Interest Entity [Line Items]
Net proceeds on sale	$ 108
Gain on sale, pretax	45us-gaap_GainOnSaleOfInvestments
Non controlling interest of third party	9us-gaap_MinorityInterest
Noncontrolling Interest [Member]
Variable Interest Entity [Line Items]
Non controlling interest of third party	9
Variable Interest Entity, Not Primary Beneficiary [Member] \| Copper Mountain Solar 3 [Member]
Variable Interest Entity [Line Items]
Percentage of variable interests	50.00%
Variable Interest Entity, Not Primary Beneficiary [Member] \| California Solar [Member]
Variable Interest Entity [Line Items]
Percentage of variable interests	50.00%
Variable Interest Entity, Not Primary Beneficiary [Member] \| Broken Bow II [Member]
Variable Interest Entity [Line Items]
Percentage of variable interests	50.00%
Variable Interest Entity, Not Primary Beneficiary [Member] \| Nevada [Member] \| Copper Mountain Solar 3 [Member]
Variable Interest Entity [Line Items]
Generating capacity	250
Variable Interest Entity, Not Primary Beneficiary [Member] \| Nebraska [Member] \| Broken Bow II [Member]
Variable Interest Entity [Line Items]
Generating capacity	75
Variable Interest Entity, Primary Beneficiary [Member] \| Texas Solar 4 [Member]
Variable Interest Entity [Line Items]
Percentage of variable interests	80.00%
Purchase of membership interest, amount	49
Net assets	58
Variable Interest Entity, Primary Beneficiary [Member] \| Texas Solar 4 [Member] \| Noncontrolling Interest [Member]
Variable Interest Entity [Line Items]
Non controlling interest of third party	9
Variable Interest Entity, Primary Beneficiary [Member] \| Texas [Member] \| Texas Solar 4 [Member]
Variable Interest Entity [Line Items]
Generating capacity	40
California Solar [Member]
Variable Interest Entity [Line Items]
Percentage of variable interests sold	50.00%
Net proceeds on sale	108
Gain on sale, pretax	45
Gain on sale, net of tax	$ 26
California Solar [Member] \| California [Member]
Variable Interest Entity [Line Items]
Generating capacity	110
CECONY [Member]
Variable Interest Entity [Line Items]
Number of potential VIEs, long-term electricity purchase agreements	3

Gain Loss On Investments Net Of Tax

No definition available.

Name:	ed_GainLossOnInvestmentsNetOfTax
Namespace Prefix:	ed_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Generating Capacity

+ References

No definition available.

+ Details

Name:	ed_GeneratingCapacity
Namespace Prefix:	ed_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of potential variable interest entities.

+ References

No definition available.

+ Details

Name:	ed_NumberOfPotentialVariableInterestEntities
Namespace Prefix:	ed_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage Of Membership Interests Sold

+ References

No definition available.

+ Details

Name:	ed_PercentageOfMembershipInterestsSold
Namespace Prefix:	ed_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The difference between the carrying value and the sale price of an investment. A gain would be recognized when the sale price of the investment is greater than the carrying value of the investment. This element refers to the Gain included in earnings and not to the cash proceeds of the sale.

+ References

No definition available.

+ Details

Name:	us-gaap_GainOnSaleOfInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (that is, noncontrolling interest, previously referred to as minority interest).

+ 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 210.5-02.31)

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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 27

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 20

-Article 7

+ Details

Name:	us-gaap_MinorityInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow associated with the deconsolidation of a previously consolidated subsidiary or the sale of investment in consolidated subsidiaries (generally greater than 50 percent).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromDivestitureOfInterestInConsolidatedSubsidiaries
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The net carrying amount of the consolidated Variable Interest Entity's assets and liabilities included in the reporting entity's statement of financial position.

+ References

No definition available.

+ Details

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

- Details

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

- Definition

Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 5A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=28200181&loc=SL6759159-111685

+ Details

Name:	us-gaap_VariableInterestEntityOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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

- Details

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

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_NoncontrollingInterestMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: