Accounts Receivable (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Accounts Notes And Loans Receivable Net Current [Abstract]
Unbilled revenues	$ 1,151		$ 1,094
Allowance for uncollectible accounts	(272)		(293)
Accounts Receivable Additional Disclosures [Abstract]
Gross Accounts Receivable Pledged as Collateral	0
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables	19		18
Exelon Generation Co L L C [Member]
Accounts Notes And Loans Receivable Net Current [Abstract]
Unbilled revenues	584	[1]	535	[1]
Allowance for uncollectible accounts	(57)		(84)
Commonwealth Edison Co [Member]
Accounts Notes And Loans Receivable Net Current [Abstract]
Unbilled revenues	201		213
Allowance for uncollectible accounts	(62)		(70)
PECO Energy Co [Member]
Accounts Notes And Loans Receivable Net Current [Abstract]
Unbilled revenues	161		164
Allowance for uncollectible accounts	(107)		(99)
Accounts Notes And Loans Receivable Net Current Footnotes [Abstract]
Current financing receivable allowance for credit losses	8		7
Accounts Receivable Additional Disclosures [Abstract]
Accounts receivable, pledged under accounts receivable agreement			210
Gross Accounts Receivable Pledged as Collateral	0		289
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables uncollectible accounts reserve	(18)		(15)
PECO Energy Co [Member] | Low Risk [Member]
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables uncollectible accounts reserve	(1)		(1)
PECO Energy Co [Member] | Medium Risk [Member]
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables	4		3
PECO Energy Co [Member] | High Risk [Member]
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables	13		11
Baltimore Gas and Electric Company [Member]
Accounts Notes And Loans Receivable Net Current [Abstract]
Unbilled revenues	205		182
Allowance for uncollectible accounts	$ (46)		$ (40)

[1] Represents unbilled portion of retail receivables estimated under Exelon’s unbilled critical accounting policy