The amount remitted to variable interest entities for rate stabilization bonds.

No definition available.

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

- Definition

Megawatts acquired upon completion of the acquisition.

+ References

No definition available.

+ Details

Name:	exc_BusinessAcquisitionsMegawattsAcquired
Namespace Prefix:	exc_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of Project Entities with Noncontrolling Interests

+ References

No definition available.

+ Details

Name:	exc_NumberofProjectEntitieswithNoncontrollingInterests
Namespace Prefix:	exc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of variable interest entities (VIEs) consolidated.

+ References

No definition available.

+ Details

Name:	exc_NumberOfVariableInterestEntitiesConsolidated
Namespace Prefix:	exc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of variable interest entities (VIEs) not consolidated.

+ References

No definition available.

+ Details

Name:	exc_NumberOfVariableInterestEntitiesNotConsolidated
Namespace Prefix:	exc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Ownership Interest in Project Entities

+ References

No definition available.

+ Details

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

- Definition

Percentage of ownership interest in certain nonconsolidated VIEs where none of the equity holders consolidate these VIEs.

+ References

No definition available.

+ Details

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

- Definition

Ownership Percentage of Noncontrolling Interests in Project Entities

+ References

No definition available.

+ Details

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

- Definition

Projects with economic interest that is significantly greater than its stated power to direct activities of the project.

+ References

No definition available.

+ Details

Name:	exc_ProjectsWithSignificantEconomicPower
Namespace Prefix:	exc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

This element represents the percentage of nuclear output to be purchased by third party.

+ References

No definition available.

+ Details

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

- Definition

Represents the required purchases of power from a related party, that is not sold to third parties, over the specified term of a power purchase agreement, percent.

+ References

No definition available.

+ Details

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

- Definition

Amount charged against earnings in the period for a specified incurred and estimated severance cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

+ References

No definition available.

+ Details

Name:	exc_SeveranceObligationSeveranceCharges
Namespace Prefix:	exc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

In a business combination achieved in stages, this element represents the amount of gain recognized by the entity as a result of remeasuring to fair value the equity interest in the acquiree it held before the business combination.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (g)(2)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

+ Details

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

- Definition

Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.13,16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

- Definition

For an unclassified balance sheet, amount of receivables due from an entity that is affiliated with the reporting entity by means of direct or indirect ownership.

+ References

Reference 1: 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.(k)(1))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph k

-Subparagraph 1

-Article 4

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 3

-Article 7

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39599-107864

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.3)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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

- Definition

Amount of payable due to an entity that is affiliated with the reporting entity by means of direct or indirect ownership.

+ References

Reference 1: 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.(k)(1))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph k

-Subparagraph 1

-Article 4

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.17)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 17

-Article 7

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.6-04.12(3))

-URI http://asc.fasb.org/extlink&oid=6488278&loc=d3e603758-122996

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.15(3))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph 3

-Article 9

+ Details

Name:	us-gaap_DueToAffiliateCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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 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

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

- Definition

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

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

- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (b)(1)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=exc_ConstellationEnergyNuclearGroupMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringCostAndReserveAxis=exc_OtherSeveranceChargesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Variable Interest Entities - Narrative (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended	0 Months Ended	12 Months Ended
	Dec. 31, 2014 VIE	Apr. 01, 2014	Dec. 31, 2013	Dec. 31, 2012
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Number of variable interest entities not consolidated by equity holders	6		8
Number of variable interest entities consolidated	6		4
Consolidated Variable Interest Entity [Abstract]
Parental guarantee provided	$ 75
Required purchases of power from CENG's nuclear plants not sold to third parties	85.00%
Purchase of nuclear output by EDF	49.99%
Guarantee obligations maximum exposure	9,402
Other Severance Charges [Member]
Consolidated Variable Interest Entity [Abstract]
Severance charges recorded	6
Constellation Energy Nuclear Group [Member] \| Financial Guarantee [Member]
Consolidated Variable Interest Entity [Abstract]
Guarantee obligations maximum exposure		165
Constellation Energy Nuclear Group [Member] \| Payment Guarantee [Member]
Consolidated Variable Interest Entity [Abstract]
Due to affiliate		245
Exelon Generation Co L L C [Member]
Consolidated Variable Interest Entity [Abstract]
Parental guarantee provided	5
Ownership Percentage Of Consolidated Variable Interest Entities	100.00%
Debt and Capital Lease Obligations	7,652		7,168
Wind project entities with noncontrolling equity interests	9
Noncontrolling equity interest ownership percentage held by third parties	1.00%
Number of projects with significant economic power	8
Ownership interests in project entities	99.00%
Ownership interest	50.01%
Required purchases of power from CENG's nuclear plants not sold to third parties	85.00%	85.00%
Severance charges recorded	3
Purchase of nuclear output by EDF		49.99%
Guarantee obligations maximum exposure	6,384
Exelon Generation Co L L C [Member] \| Constellation Energy Nuclear Group [Member]
Consolidated Variable Interest Entity [Abstract]
Due from affiliates	400	400
Exelon Generation Co L L C [Member] \| Constellation Energy Nuclear Group [Member] \| Payment Guarantee [Member]
Consolidated Variable Interest Entity [Abstract]
Due to affiliate		205
Exelon Generation Co L L C [Member] \| Solar Project Limited Liability Companies [Member]
Consolidated Variable Interest Entity [Abstract]
Business Acquisitions, Megawatts Acquired	242
Ownership Percentage Of Consolidated Variable Interest Entities	100.00%
Debt and Capital Lease Obligations	642
Exelon Generation Co L L C [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Consolidated Variable Interest Entity [Abstract]
Parental guarantee provided	7	7
Remeasurement gain from derecognition of equity method investment		261
Exelon Generation Co L L C [Member] \| Variable Interest Entity, Primary Beneficiary [Member] \| Equity Method Investment Variable Interest Entities [Member]
Consolidated Variable Interest Entity [Abstract]
Parental guarantee provided	637
Baltimore Gas and Electric Company [Member]
Consolidated Variable Interest Entity [Abstract]
Debt and Capital Lease Obligations			2,011
Guarantee obligations maximum exposure	265
Baltimore Gas and Electric Company [Member] \| RSB Bond Co LLC [Member]
Consolidated Variable Interest Entity [Abstract]
Remittance of payments received from customers for rate stabilization to BondCo.	$ 85		$ 83	$ 85