Derivative Instruments and Hedging Activities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Investment Holdings [Line Items]
Energy supply and hedging activities credit exposure total	$ 113
Makeup of net credit exposure, with investment-grade counterparties	41
Makeup of net credit exposure with commodity exchange brokers	41
Makeup of net credit exposure independent system operators	28
Makeup of net credit exposure non-investment grade/non-rated counterparties	3
Number of contracts considered derivatives	1147
Collateral posted
Additional Collateral Required Due To Loss Of Unsecured Credit [Member]
Investment Holdings [Line Items]
Collateral posted	24
Additional collateral aggregate fair value down below investment grade [Member]
Investment Holdings [Line Items]
Collateral posted	24
Purchased power expense [Member]
Investment Holdings [Line Items]
Unrealized gain (loss) on derivatives	82	(34)
Non-utility revenue [Member]
Investment Holdings [Line Items]
Unrealized gain (loss) on derivatives	(14)	11
CECONY [Member]
Investment Holdings [Line Items]
Energy supply and hedging activities credit exposure total	19
Makeup of net credit exposure, with investment-grade counterparties	1
Makeup of net credit exposure with commodity exchange brokers	18
Number of contracts considered derivatives	581
Collateral posted
CECONY [Member] \| Additional Collateral Required Due To Loss Of Unsecured Credit [Member]
Investment Holdings [Line Items]
Collateral posted	10
CECONY [Member] \| Additional collateral aggregate fair value down below investment grade [Member]
Investment Holdings [Line Items]
Collateral posted	1
Interest Rate Swap [Member]
Investment Holdings [Line Items]
Unrealized gain (loss) on derivatives	6
Derivative, fixed interest rate	6.09%
Increase in the fair value of derivative	$ 2

Change In Fair Value Of Interest Rate Swaps

No definition available.

Name:	ed_ChangeInFairValueOfInterestRateSwaps
Namespace Prefix:	ed_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Credit Exposure Independent System Operators

+ References

No definition available.

+ Details

Name:	ed_CreditExposureIndependentSystemOperators
Namespace Prefix:	ed_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Credit exposure nonrated counterparties

+ References

No definition available.

+ Details

Name:	ed_CreditExposureNonratedCounterParties
Namespace Prefix:	ed_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Maximum Potential Future Exposure On Credit Risk Derivatives Total

+ References

No definition available.

+ Details

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

- Definition

Maximum Potential Future Exposure On Credit Risk Derivatives With Commodity Exchange Brokers

+ References

No definition available.

+ Details

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

- Definition

Maximum Potential Future Exposure On Credit Risk Derivatives With Investment Grade Counterparties

+ References

No definition available.

+ Details

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

- Definition

The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44D

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4H

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624258-113959

+ Details

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

- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeFixedInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Information that would enable users to understand the volume of the entity's derivative activity.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5579245-113959

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5580258-113959

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44

-Subparagraph 2

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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

- Details

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

- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

+ Details

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