Regulatory Matters - Energy Efficiency Formula Rate (Details) - Commonwealth Edison Co [Member] - ComEd 2020 Energy Efficiency Formula Rate [Domain] - USD ($) $ in Millions		12 Months Ended
Jun. 01, 2021	Dec. 31, 2020
Schedule of Energy Efficiency Formula Rate Updates [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 55
Revenue	(1)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	$ 54
Public Utilities, Requested Equity Capital Structure, Percentage	5.72%
Requested Return on Equity, Percentage	7.36%
Basis points for ComEd's Revenue Requirement	580
Public Utilities, Approved Equity Capital Structure, Percentage		6.26%
Public Utilities, Approved Return on Equity, Percentage		8.46%

- Definition

Maximum basis points that can be added to the average rate on 30-year treasury notes, to determine the allowed ROE for ComEd's revenue requirement.

+ References

No definition available.

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

[Line Items] for Schedule of Energy Efficiency Formula Rate Updates [Table]

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

Percentage of public utility's approved return on equity.

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

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- Definition

Percentage of public utility's requested return on equity.

+ References

No definition available.

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