Accounts Receivable - Schedule of Estimated Unbilled Revenues (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues	$ 1,381		$ 1,151
Allowance for uncollectible accounts	(311)	[1]	(272)	[1]
Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues	823	[2]	584	[2]
Allowance for uncollectible accounts	(60)	[1]	(57)	[1]
Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues	204		201
Allowance for uncollectible accounts	(84)	[1]	(62)	[1]
PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues	140		161
Allowance for uncollectible accounts	(100)	[1],[3]	(107)	[1],[3]
Current financing receivable allowance for credit losses	7		8
Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues	214		205
Allowance for uncollectible accounts	(67)	[1],[4]	(46)	[1],[4]
Charged to Costs and Expenses	$ 19

[1] Includes the allowance for uncollectible accounts on customer and other accounts receivable.

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

[3] Includes an allowance for uncollectible accounts of $7 million and $8 million at December 31, 2014 and 2013, respectively, related to PECO’s current installment plan receivables described below.

[4] At December 31, 2014, as explained in Note 1—Significant Accounting Policies, BGE estimated the allowance for uncollectible accounts on customer receivables by applying loss rates to the outstanding receivable balance by risk segment. The change in estimate resulted in a $19 million pre-tax charge to BGE's provision for uncollectible accounts expense for the year ended December 31, 2014, which is included in Operating and maintenance expense on BGE's Consolidated Statements of Operations and Comprehensive Income.