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Severance - Ongoing Severance Plans (Details) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Corporate Restructuring Severance Benefit Obligation [Line Items]    
Severance charges recorded $ 20exc_SeveranceObligationSeveranceCharges $ 4exc_SeveranceObligationSeveranceCharges
Exelon Generation Co L L C [Member]    
Corporate Restructuring Severance Benefit Obligation [Line Items]    
Severance charges recorded 20exc_SeveranceObligationSeveranceCharges
/ dei_LegalEntityAxis
= exc_ExelonGenerationCoLLCMember		 4exc_SeveranceObligationSeveranceCharges
/ dei_LegalEntityAxis
= exc_ExelonGenerationCoLLCMember
Commonwealth Edison Co [Member]    
Corporate Restructuring Severance Benefit Obligation [Line Items]    
Severance charges recorded 0exc_SeveranceObligationSeveranceCharges
/ dei_LegalEntityAxis
= exc_CommonwealthEdisonCoMember		 0exc_SeveranceObligationSeveranceCharges
/ dei_LegalEntityAxis
= exc_CommonwealthEdisonCoMember
PECO Energy Co [Member]    
Corporate Restructuring Severance Benefit Obligation [Line Items]    
Severance charges recorded 0exc_SeveranceObligationSeveranceCharges
/ dei_LegalEntityAxis
= exc_PecoEnergyCoMember		 0exc_SeveranceObligationSeveranceCharges
/ dei_LegalEntityAxis
= exc_PecoEnergyCoMember
Baltimore Gas and Electric Company [Member]    
Corporate Restructuring Severance Benefit Obligation [Line Items]    
Severance charges recorded $ 0exc_SeveranceObligationSeveranceCharges
/ dei_LegalEntityAxis
= exc_BaltimoreGasAndElectricCompanyMember		 $ 0exc_SeveranceObligationSeveranceCharges
/ dei_LegalEntityAxis
= exc_BaltimoreGasAndElectricCompanyMember