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

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

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

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Percentage of public utility's approved return on equity.

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

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No definition available.

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

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

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Percentage of public utility's requested return on equity.

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Regulatory Matters Energy Efficiency Formula Rate (Details) - Commonwealth Edison Co [Member] - USD ($) $ in Millions					6 Months Ended	12 Months Ended
	May 23, 2019	Apr. 08, 2019	Dec. 04, 2018	Apr. 16, 2018	Jun. 30, 2019	Dec. 31, 2018
Schedule of Energy Efficiency Formula Rate Updates [Line Items]
Initial Revenue Requirement Increase (Decrease)	$ 53				$ 21
Annual Reconciliation Increase (Decrease)	(2)				(16)
Total Revenue Requirement Increase (Decrease)	$ 51				$ 5
Requested Return on Equity, Percentage	8.91%
Allowed Return on Equity, Percentage					11.50%	10.91%
Allowed Return on Rate Base, Percentage					8.21%
Electric Distribution [Member]
Schedule of Energy Efficiency Formula Rate Updates [Line Items]
Initial Revenue Requirement Increase (Decrease)		$ (6)		$ (23)	$ 57
Requested Return on Distribution Rate Base, Percentage	6.53%					6.53%
Requested Return on Equity, Percentage		8.91%
Allowed Return on Equity, Percentage			8.69%
Allowed Return on Rate Base, Percentage						7.49%