Income Tax - Income Tax Reconciliation (Details)	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
STATUTORY TAX RATE
Federal	21.00%	35.00%
Changes in computed taxes resulting from:
State income tax	4.00%	4.00%
Cost of removal	1.00%	1.00%
Other plant-related items	0.00%	0.00%
Change in deferred taxes	0.00%	(1.00%)
Renewable energy credits	(1.00%)	(1.00%)
Amortization of excess deferred federal income taxes	(3.00%)	(0.00%)
Other	(1.00%)	(1.00%)
Effective tax rate	21.00%	37.00%
CECONY
STATUTORY TAX RATE
Federal	21.00%	35.00%
Changes in computed taxes resulting from:
State income tax	5.00%	4.00%
Cost of removal	1.00%	1.00%
Other plant-related items	(1.00%)	(1.00%)
Change in deferred taxes	0.00%	0.00%
Renewable energy credits	(0.00%)	(0.00%)
Amortization of excess deferred federal income taxes	(3.00%)	(0.00%)
Other	0.00%	0.00%
Effective tax rate	23.00%	39.00%

Effective Income Tax Rate Reconciliation, cost of removal

No definition available.

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

- Definition

Effective Income Tax Rate Reconciliation, Other Plant-Related Items, Percent

+ References

No definition available.

+ Details

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

- Definition

Effective Income Tax Rate Reconciliation, Tax Credit, Renewable Energy Credits, Percent

+ References

No definition available.

+ Details

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

- Definition

Effective Income Tax Rate Reconciliation, Tax Cuts And Jobs Act Of 2017, Percent

+ References

No definition available.

+ Details

Name:	ed_EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017Percent
Namespace Prefix:	ed_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Federal Statutory Income Tax Rate [Abstract]

+ References

No definition available.

+ Details

Name:	ed_FederalStatutoryIncomeTaxRateAbstract
Namespace Prefix:	ed_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I)
-URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

+ Details

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

- Definition

Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other adjustments.

+ References

+ Details

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

- Definition

+ References

+ Details

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

- Definition

+ References

+ Details

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

- Details

Name:	dei_LegalEntityAxis=ed_ConsolidatedEdisonCompanyofNewYorkInc.Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: