Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2011
Consolidation Percentages Detail Tagging [Abstract]
Percentage ownership of consolidated subsidiaries	100.00%
Exelon Percentage ownership of Exelon SHC, LLC	1.00%
Percentage ownership of ComEd's common stock	99.00%
Percentage ownership of PECO's common stock	100.00%
Third-party interest in ComEd - exclusive upper bound	$ 1
Exelon Generation Co L L C [Member]
Consolidation Percentages Detail Tagging [Abstract]
Percentage ownership of consolidated subsidiaries	100.00%
Generation Percentage ownership of Exelon SHC, LLC	99.00%
Ownership Interest Upper Bound	99.00%
Ownership Interest Lower Bound	94.00%

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

Name:	exc_ConsolidatedSubsidiaryCommonStockOwnershipPercentage
Namespace Prefix:	exc
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ Details

Name:	exc_ConsolidatedSubsidiaryOwnershipPercentage
Namespace Prefix:	exc
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Consolidated subsidiaries ownership percentage information detail tagging abstract.

+ Details

Name:	exc_ConsolidationPercentagesDetailTaggingAbstract
Namespace Prefix:	exc
Data Type:	xbrli:stringItemType
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 (noncontrolling interest, minority interest) did not exceed this amount.

+ Details

Name:	exc_MinorityInterestUpperBound
Namespace Prefix:	exc
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Generation ownership interest in certain Exelon Wind Projects lower bound.

+ Details

Name:	exc_OwnershipInterestLowerBound
Namespace Prefix:	exc
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Generation ownership interest in certain Exelon Wind Projects upper bound.

+ Details

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

- 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 Statement of Financial Accounting Standard (FAS)

-Number 159

-Paragraph 18

-Subparagraph f

-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 AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 20

-Subparagraph a (1)

-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 3: 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

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

+ Details

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

- Definition

The number of units or percentage investment held in the subsidiary by the limited liability company or limited partnership.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 22

-Article 12

+ Details

Name:	us-gaap_SubsidiaryOfLimitedLiabilityCompanyOrLimitedPartnershipOwnershipInterest
Namespace Prefix:	us-gaap
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration