Accounts Receivable (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Accounts Notes And Loans Receivable Net Current [Abstract]
Allowance for uncollectible accounts	$ 306	$ 272
Accounts Receivable Additional Disclosures [Abstract]
Gross Accounts Receivable Pledged as Collateral	0	0
Exelon Generation Co L L C [Member]
Accounts Notes And Loans Receivable Net Current [Abstract]
Allowance for uncollectible accounts	46	57
Commonwealth Edison Co [Member]
Accounts Notes And Loans Receivable Net Current [Abstract]
Allowance for uncollectible accounts	76	62
PECO Energy Co [Member]
Accounts Notes And Loans Receivable Net Current [Abstract]
Allowance for uncollectible accounts	140	107
Accounts Receivable Additional Disclosures [Abstract]
Gross Accounts Receivable Pledged as Collateral	0	0
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables	18	19
Installment plan receivables uncollectible accounts reserve	(15)	(18)
PECO Energy Co [Member] | Medium Risk [Member]
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables uncollectible accounts reserve	(4)	(4)
PECO Energy Co [Member] | High Risk [Member]
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables uncollectible accounts reserve	(10)	(13)
Baltimore Gas and Electric Company [Member]
Accounts Notes And Loans Receivable Net Current [Abstract]
Allowance for uncollectible accounts	$ 44	$ 46