Assumed annual after-tax returns for former PECO units used in calculating NRC minimum requirements.

No definition available.

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Namespace Prefix:	exc_
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Balance Type:	na
Period Type:	duration

- Definition

Assumed annual after-tax returns used in calculating NRC minimum requirements.

+ References

No definition available.

+ Details

Name:	exc_AnnualAfterTaxReturnOnNuclearDecommissioningFund1
Namespace Prefix:	exc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Historical five-year annual average after-tax return on NDT funds

+ References

No definition available.

+ Details

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

- Definition

Percent of annual average accretion of the ARO used in the NRC minimum funding requirements.

+ References

No definition available.

+ Details

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

- Details

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- Definition

Amount of decommissioning shortfall with recourse for collection from customers.

+ References

No definition available.

+ Details

Name:	exc_DecommissioningShortfall
Namespace Prefix:	exc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percent of additional decommissioning shortfall with recourse for collection from customers.

+ References

No definition available.

+ Details

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

- Definition

Estimated lower bound of the annual after-tax return on NDT funds used in the NRC minimum funding requirements.

+ References

No definition available.

+ Details

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

- Definition

Estimated upper bound of annual after-tax return on NDT funds used in the NRC minimum funding requirements.

+ References

No definition available.

+ Details

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

- Definition

Amount provided under letter of credit by EnergySolutions to reduce risk of default under the assets sale agreement and to be used to fund decommissioning costs in the event the NDT assets are insufficient.

+ References

No definition available.

+ Details

Name:	exc_LetterOfCreditUsedToFundDecommissioningCosts
Namespace Prefix:	exc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Guarantees established and provided by the Parent Company to cover the NRC underfunded position.

+ References

No definition available.

+ Details

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

- Definition

Current annual recovery of nuclear decommissioning costs from customers filed with state regulator

+ References

No definition available.

+ Details

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

- Definition

Percentage of nuclear decommissioning trust funds invested in equity.

+ References

No definition available.

+ Details

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

- Definition

Percentage of nuclear decommissioning trust funds invested in fixed income securities.

+ References

No definition available.

+ Details

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

- Definition

Number of Operating Reactors

+ References

No definition available.

+ Details

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

- Definition

Number of years that measurement of the obligation at the present value of the future estimated costs and an annual average accretion of the ARO occurs.

+ References

No definition available.

+ Details

Name:	exc_NumberOfYearsUsedInPresentValueMeasurement
Namespace Prefix:	exc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Provision for the disposal costs of spent nuclear fuel from ZionStation which was retained as part of the asset sale agreement.

+ References

No definition available.

+ Details

Name:	exc_SpentNuclearFuelObligation
Namespace Prefix:	exc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Years after the cessation of plant operations when consideration of multiple scenarios where decommissioning activities are completed under three possible scenarios.

+ References

No definition available.

+ Details

Name:	exc_YearsAfterCessationOfPlantOperations
Namespace Prefix:	exc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable for contractual rent under lease arrangements.

+ References

Reference 1: 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(5))

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph a

-Article 7

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph 5

-Article 9

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 210.9-03.15(5))

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

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- Definition

Net Increase or Decrease in the asset retirement obligation during the period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

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- Definition

Amount of the Increase or Decrease in the amount of the asset retirement obligation during the current period for changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 410

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (c)(4)

-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

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- Definition

Decommission fund to pay for the costs of decontaminating and decommissioning of facilities through collection of revenues derived from utility assessments and government appropriations. Decommission fund investment for the process whereby a power station, at the end of its economic life, is taken permanently out of service and its site made available for other purposes. In the case of a nuclear station this comprises three different states of clearance. Immediately after the final closure, radioactive material such as nuclear fuel and operational waste is removed and the buildings surrounding the reactor shield are dismantled and finally the reactor itself is dismantled.

+ 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 210.5-02.12)

-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 12

-Article 5

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Details

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Asset Retirement Obligations - Narrative (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Oct. 02, 2013 reactor	Dec. 31, 2012
Asset Retirement Obligations [Line Items]
Nuclear decommissioning annual recovery current	$ 24,000,000
Percent of additional decommissioning shortfall with recourse	50.00%exc_DecommissioningShortfallPercentage
Nuclear decommissioning trust funds	10,537,000,000us-gaap_DecommissioningFundInvestments	8,071,000,000us-gaap_DecommissioningFundInvestments
Minimum [Member]
Asset Retirement Obligations [Line Items]
Years after cessation of plant operations	20 years
Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Increase (decrease) in asset retirement obligation	2,100,000,000	114,000,000
Shortfall of decommissioning funds with recourse	50,000,000
Percent of additional decommissioning shortfall with recourse	5.00%
Nuclear decommissioning trust funds	10,537,000,000	8,071,000,000
Percent of NDT funds invested in equity	52.00%	48.00%
Percent of NDT funds invested in fixed income securities	48.00%	52.00%
Zion Station spent nuclear fuel obligation	86,000,000
ZionSolutions rent payable	1
EnergySolutions letter of credit	200,000,000
Assumed annual after-tax return on NDT funds	2.00%
Assumed annual after-tax return on NDT funds for former PECO units	3.00%
Annual average accretion of the ARO	5.00%
Number of years used in present value measurement	30 years
Estimated annual after tax return on nuclear decommissioning funds lower bound	6.00%
Estimated annual after tax return on nuclear decommissioning funds upper bound	6.30%
Historical five-year annual average after-tax return on NDT funds	9.00%
NRC funding assurance parent guarantees				115,000,000
Number of operating reactors			104
Exelon Generation Co L L C [Member] \| Minimum [Member]
Asset Retirement Obligations [Line Items]
Years after cessation of plant operations	10 years
Exelon Generation Co L L C [Member] \| Maximum [Member]
Asset Retirement Obligations [Line Items]
Years after cessation of plant operations	70 years
Nuclear Decommissioning Asset Retirement Obligation [Member] \| Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Net increase (decrease) resulting from updates to estimated future cash flows	19,000,000	(140,000,000)
Property, Plant and Equipment [Member] \| Nuclear Decommissioning Asset Retirement Obligation [Member] \| Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Net increase (decrease) resulting from updates to estimated future cash flows	$ 16,000,000