Regulatory Matters - Annual Electric Transmission Fillings (Details) - Commonwealth Edison Co [Member] - 2021 Transmission Formula Rate Annual Update [Domain] $ in Millions	Apr. 16, 2021 USD ($)
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 33
Annual Reconciliation Decrease	12
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	$ 45
Public Utilities, Approved Equity Capital Structure, Percentage	8.20%
Public Utilities, Approved Return on Equity, Percentage	11.50%
Cap on Equity Component of Rate of Return on Common Equity in Federal Energy Regulatory Committee Complaint	55.00%

- Definition

The maximum percentage allowed for the equity component of the rate of return on common equity in the Federal Energy Regulatory Committee Complaint.

+ References

No definition available.

+ Details

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

- Definition

Exepected adjustment to revenue to be recorded in the prior year.

+ References

No definition available.

+ Details

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

- Definition

Percentage of public utility's approved equity to capital, including debt and equity.

+ References

No definition available.

+ Details

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

- Definition

Percentage of public utility's approved return on equity.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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.

+ References

No definition available.

+ Details

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

- Definition

Amount of public utility's amended requested rate increase (decrease) with regulatory agency.

+ References

No definition available.

+ Details

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

- Definition

Amount of public utility's requested rate increase (decrease) with regulatory agency.

+ References

No definition available.

+ Details

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

- Details

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

- Details

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