Mergers, Acquisitions and Dispositions - Costs Recognized after Closing of Merger (Details) $ in Millions	12 Months Ended
	Dec. 31, 2013 USD ($) $ / Customer
Business Acquisition [Line Items]
Rate credit per residential customer (in usd per customer) | $ / Customer	100
Charitable contributions, per year | $	$ 7
Period for charitable contributions	10 years
Baltimore Gas and Electric Company [Member]
Business Acquisition [Line Items]
Rate credit per residential customer (in usd per customer) | $ / Customer	100
Charitable contributions, per year | $	$ 7
Period for charitable contributions	10 years
Exelon Generation Co L L C [Member]
Business Acquisition [Line Items]
Rate credit per residential customer (in usd per customer) | $ / Customer	100
Charitable contributions, per year | $	$ 7
Period for charitable contributions	10 years