Impairment of Long-Lived Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Capital Leases, Net Investment in Direct Financing Leases, Unguaranteed Residual Values of Leased Property	$ 1,465		$ 1,492
Less: unearned income	(767)		(807)
Net investment in long-term leases	698		685
Tangible Asset Impairment Charges	43
CapitalLeaseNetInvestmentInDirectFinancingLeasesPrepaymentsReceived	1,200
Utilities Operating Expense Maintenance And Operations [Abstract]
Utilities Operating Expense, Impairments	111
Interest Costs Incurred [Abstract]
Interest Costs Incurred			1,003	[1]	783	[1]
Exelon Generation Co L L C [Member]
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Net investment in long-term leases	693
Interest Costs Incurred [Abstract]
Interest Costs Incurred	411	[1]	368	[1]	219	[1]
Commonwealth Edison Co [Member]
Interest Costs Incurred [Abstract]
Interest Costs Incurred	584	[1]	310	[1]	349	[1]
PECO Energy Co [Member]
Interest Costs Incurred [Abstract]
Interest Costs Incurred	117	[1]	125	[1]	138	[1]
Baltimore Gas and Electric Company [Member]
Interest Costs Incurred [Abstract]
Interest Costs Incurred	$ 129	[1]	$ 149	[1]	$ 136	[1]

[1] Exelon activity for the year ended December 31, 2012 includes the results of Constellation and BGE for March 12, 2012 – December 31, 2012. Generation activity for the year ended December 31, 2012 includes the results of Constellation for March 12, 2012 – December 31, 2012. BGE activity represents the activity for the years ended December 31, 2012, 2011 and 2010. (b)        Includes interest expense to affiliates.