Accounts Receivable (Details) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Accounts Notes And Loans Receivable Net Current [Abstract]
Allowance for uncollectible accounts	$ (303,000,000)	$ (199,000,000)
Accounts Receivable Additional Disclosures [Abstract]
Gross Accounts Receivable Pledged as Collateral	296,000,000	329,000,000
Exelon Generation Co L L C [Member]
Accounts Notes And Loans Receivable Net Current [Abstract]
Allowance for uncollectible accounts	(91,000,000)	(29,000,000)
Commonwealth Edison Co [Member]
Accounts Notes And Loans Receivable Net Current [Abstract]
Allowance for uncollectible accounts	(78,000,000)	(78,000,000)
PECO Energy Co [Member]
Accounts Notes And Loans Receivable Net Current [Abstract]
Allowance for uncollectible accounts	(102,000,000)	(92,000,000)
Accounts Receivable Additional Disclosures [Abstract]
Gross Accounts Receivable Pledged as Collateral	296,000,000	329,000,000
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables	21,000,000	21,000,000
Installment plan receivables uncollectible accounts reserve	(18,000,000)	(17,000,000)
PECO Energy Co [Member] | Low To Medium Risk [Member]
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables uncollectible accounts reserve	(1,000,000)	(1,000,000)
PECO Energy Co [Member] | Medium Risk [Member]
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables uncollectible accounts reserve	(4,000,000)	(3,000,000)
PECO Energy Co [Member] | High Risk [Member]
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables uncollectible accounts reserve	(13,000,000)	(13,000,000)
Baltimore Gas and Electric Company [Member]
Accounts Notes And Loans Receivable Net Current [Abstract]
Allowance for uncollectible accounts	$ (32,000,000)	$ (38,000,000)