Retirement Benefits - Defined Contribution Savings Plans (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	$ 20	$ 20
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	8	8
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	3	3
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	2	2
Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	3	3
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	1	1
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	1	1
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plans Matching Contributions	$ 0	$ 0

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Name:	us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration