Additional guarantees potentially required by the Parent Company to cover the NRC underfunded position.

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- Definition

Fair value as of the balance sheet date of cash and non-cash collateral held for loan securities

+ Details

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Namespace Prefix:	exc
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

The weighted average maturity in months of the securities purchased with funds received as collateral.

+ Details

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- Definition

Current amount of liability as of the balance sheet date associated with the asset sale agreement and transfer of asset retirement obligation to ZionSolutions, included in Other Current Liabilities on the Balance Sheet.

+ Details

Name:	exc_CurrentPayableToZionsolutions
Namespace Prefix:	exc
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Balance Type:	credit
Period Type:	instant

- Details

Name:	exc_FootnotesToNuclearDecommissioningAssetRetirementObligationAbstract
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- Details

Name:	exc_FootnotesToUnrealizedGainsLossesOnNdtFundsAbstract
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Data Type:	xbrli:stringItemType
Balance Type:	na
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- Definition

Total gross amount of liability as of the balance sheet date associated with the asset sale agreement and transfer of asset retirement obligation to ZionSolutions.

+ Details

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Namespace Prefix:	exc
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- Definition

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

+ Details

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Namespace Prefix:	exc
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

NRC minimum funding requirements abstract.

+ Details

Name:	exc_NrcMinimumFundingRequirementsAbstract
Namespace Prefix:	exc
Data Type:	xbrli:stringItemType
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- Definition

The carrying amount of a liability for a nuclear asset retirement obligation. A nuclear asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived nuclear asset that results from the acquisition, construction or development, or the normal operations of a nuclear long-lived asset, except for certain obligations of lessees.

+ Details

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Namespace Prefix:	exc
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Period Type:	instant

- Definition

Amount of nuclear accretion expense recognized in the income statement during the period that is associated with nuclear asset retirement obligations. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability. Such accretion expense representing changes in the liability for a nuclear asset retirement obligation due to passage of time is the result of applying an interest method of allocation to the amount of the liability at the beginning of the period. The interest rate used to measure that change shall be the credit-adjusted risk-free rate that existed when the liability, or portion thereof, was initially measured. That amount shall be recognized as an increase in the carrying amount of the liability and as an expense classified as an operating item in the statement of income. Accretion expense shall not be considered to be interest cost for purposes of capitalization of interest.

+ Details

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- Definition

Amount of nuclear asset retirement obligations settled, or otherwise disposed of, during the period. This may include nuclear asset retirement obligations transferred to third parties associated with the sale of a long-lived asset.

+ Details

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Namespace Prefix:	exc
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Period Type:	duration

- Details

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Namespace Prefix:	exc
Data Type:	xbrli:stringItemType
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- Definition

Nuclear decommissioning trust fund investments abstract.

+ Details

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Namespace Prefix:	exc
Data Type:	xbrli:stringItemType
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Period Type:	duration

- Definition

Initial minimum level of collateral required to be posted by borrowers pursuant to a security lending agreement to secure a loan for securities denominated in US currency. Percentage is based on the market value of the borrowed securities.

+ Details

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Namespace Prefix:	exc
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Initial minimum level of collateral required to be posted by borrowers pursuant to a security lending agreement to secure a loan for securities denominated in foreign currency. Percentage is based on the market value of the borrowed securities.

+ Details

Name:	exc_PercentageOfCollateralForBorrowedSecuritiesInForeignCurrency
Namespace Prefix:	exc
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The minimum required carrying amount at any point in time of cash and non-cash collateral held by borrowers as a percentage of the market value of the borrowed securities pursuant to a securities lending agreement.

+ Details

Name:	exc_PercentageOfCollateralForBorrowedSecuritiesRequiredLevels
Namespace Prefix:	exc
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Securities lending program abstract.

+ Details

Name:	exc_SecuritiesLendingProgramAbstract
Namespace Prefix:	exc
Data Type:	xbrli:stringItemType
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.

+ Details

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

- Definition

This item represents unrealized gains (losses) included in earnings for the period as a result of holding marketable securities held in nuclear decommissioning trust funds and classified as trading securities.

+ Details

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Namespace Prefix:	exc
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This item represents unrealized gains (losses) for the period as a result of holding marketable securities held in nuclear decommissioning trust funds and classified as trading securities. As a result of certain regulatory agreements for these nuclear decommissioning trust funds; upon completion of decommissioning activities, excess (shortfall of) funds will be refunded to (recovered from) rate payers through a regulated affiliate. Therefore, this activity is contractually eliminated within the income statement.

+ Details

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Namespace Prefix:	exc
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This item represents unrealized gains (losses) for the period as a result of holding marketable securities held related to the Zion Station pledged assets and classified as trading securities.

+ Details

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Namespace Prefix:	exc
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

Name:	exc_UnrealizedLossesOnNuclearDecommissioningTrustFundInvestmentLineItems
Namespace Prefix:	exc
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	exc_ZionStationDecommissioningAbstract
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- Definition

Current portion of the carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 143
-Paragraph 3, 10, 22

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

The amount of cash, securities, or other assets held by a third-party trustee pursuant to the terms of an agreement which assets are available to be used by beneficiaries to that agreement only within the specific terms thereof and which agreement is expected to terminate more than one year from the balance sheet date (or operating cycle, if longer) at which time the assets held-in-trust will be released or forfeited.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 140
-Paragraph 17
-Subparagraph c

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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 SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 12
-Article 5

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

The carrying value as of the balance sheet date of securities loaned to other broker dealers, typically used by such parties to cover short sales, secured by cash or other securities furnished by such parties until the borrowing is closed.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 140
-Paragraph 17
-Subparagraph a

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Audit and Accounting Guide (AAG)
-Number AAG-BRD
-Chapter 4
-Paragraph 32
-IssueDate 2006-05-01

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 140
-Paragraph 91, 93

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant