The percentage of ownership of common stock or equity participation in the consolidated subsidiary.

No definition available.

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Namespace Prefix:	exc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Costs per kWh of net nuclear generation required to be paid to the Department of Energy per contracts under the Nuclear Waste Policy Act of 1982. Cost can be adjusted prospectively in order to ensure full cost recovery.

+ References

No definition available.

+ Details

Name:	exc_CostOfSpentNuclearFuelDisposal
Namespace Prefix:	exc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents development costs that are expensed as incurred or previously capitalized development costs charged to operating and maintenance expense when project completion is no longer probable.

+ References

No definition available.

+ Details

Name:	exc_DevelopmentCostsExpensed
Namespace Prefix:	exc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Minimum Expectation Of Tax Position To Be Realized

+ References

No definition available.

+ Details

Name:	exc_MinimumExpectationOfTaxPositionToBeRealized
Namespace Prefix:	exc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Generation ownership interest in certain Exelon Wind Projects upper bound.

+ References

No definition available.

+ Details

Name:	exc_OwnershipInterestUpperBound
Namespace Prefix:	exc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	exc_SignificantAccountingPoliciesAdditionalNarrativeInformationLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

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

- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
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

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

- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

+ Details

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

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

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

- Definition

Percentage of subsidiary's or equity method investee's stock owned by parent immediately after all stock transactions.

+ References

No definition available.

+ Details

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

- Details

Name:	dei_LegalEntityAxis=exc_CommonwealthEdisonCoMember
Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=exc_ExelonGenerationCoLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
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- Details

Name:	exc_SubsidiaryCompaniesAxis=exc_CommonwealthEdisonCompanyMember
Namespace Prefix:
Data Type:	na
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- Details

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Namespace Prefix:
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- Details

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- Details

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Significant Accounting Policies - Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Significant Accounting Policies Additional Narrative Information [Line Items]
Percentage ownership of consolidated subsidiaries	100.00%
Percentage ownership of common stock	100.00%
Third Party interest in ComEd (less than $1 million)	$ 1,332,000,000us-gaap_MinorityInterest	$ 15,000,000us-gaap_MinorityInterest
Minimum expectation of tax position to be realized	50.00%
Commonwealth Edison Company [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
Percentage ownership of consolidated subsidiaries	99.00%
Third Party interest in ComEd (less than $1 million)	1,000,000	1,000,000
CENG [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
Ownership interest	50.01%
RITELine Illinois LLC [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
Third Party interest in ComEd (less than $1 million)	1,000,000	1,000,000
Minority interest ownership percentage by parent	12.50%
Exelon Generation Co L L C [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
Third Party interest in ComEd (less than $1 million)	1,333,000,000	17,000,000
Ownership interest upper bound	99.00%
Ownership interest	50.01%
Cost of spent nuclear fuel disposal per kWh of net nuclear generation	(0.001)
Development costs expensed	$ 13,000,000	$ 10,000,000	$ 4,000,000
Commonwealth Edison Co [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
Percentage ownership of consolidated subsidiaries	100.00%
Commonwealth Edison Co [Member] \| RITELine Illinois LLC [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
Percentage ownership of consolidated subsidiaries	75.00%
Third-party percentage interest in subsidiaries	25.00%
Minimum [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
Ownership interest	20.00%
Maximum [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
Ownership interest	50.00%
Nuclear-Fuel Generating Facilities License Extension [Member] \| Exelon Generation Co L L C [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
Useful life	20 years