Label	Element	Value
Merger Integration Costs [Member]
Regulatory Asset Recovery, Period One	exc_RegulatoryAssetRecoveryPeriodOne	$ 4,000,000
Regulatory Asset Recovery, Period Two	exc_RegulatoryAssetRecoveryPeriodTwo	$ 4,000,000
Non-severance Merger Integration Costs [Member]
Regulatory Asset, Amortization Period	us-gaap_RegulatoryAssetAmortizationPeriod	5 years
Regulatory Assets	us-gaap_RegulatoryAssets	$ 4,000,000
Baltimore Gas and Electric Company [Member] | Pension and Other Postretirement Benefits [Member]
Regulatory Asset, Amortization Period	us-gaap_RegulatoryAssetAmortizationPeriod	12 years
Baltimore Gas and Electric Company [Member] | Transmission Rate Formula [Member]
Net Regulatory Assets	us-gaap_NetRegulatoryAssets	$ 1,000,000
Net Regulatory Assets	us-gaap_NetRegulatoryAssets	12,000,000
Regulatory Assets	us-gaap_RegulatoryAssets	12,000,000
Commonwealth Edison Co [Member] | Transmission Rate Formula [Member]
Net Regulatory Assets	us-gaap_NetRegulatoryAssets	21,000,000
Net Regulatory Assets	us-gaap_NetRegulatoryAssets	31,000,000
Commonwealth Edison Co [Member] | Under Recovered Distribution Service Costs [Member]
Net Regulatory Asset	exc_NetRegulatoryAsset	371,000,000
Net Regulatory Asset	exc_NetRegulatoryAsset	189,000,000
Common Stock [Member]
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options	us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOptions	$ (3,000,000)