Impairment of Long-Lived Assets (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Sep. 30, 2013
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Capital Leases, Net Investment in Direct Financing Leases, Unguaranteed Residual Values of Leased Property	$ 1,600,000,000		$ 1,600,000,000
Tangible Asset Impairment Charges			14,000,000
CapitalLeaseNetInvestmentInDirectFinancingLeasesPrepaymentsReceived	1,200,000,000		1,200,000,000
Utilities Operating Expense Maintenance And Operations [Abstract]
Utilities Operating Expense, Impairments	92,000,000	21,000,000
Interest Costs Incurred [Abstract]
Interest Costs Incurred	8,000,000
Exelon Generation Co L L C [Member]
Utilities Operating Expense Maintenance And Operations [Abstract]
Utilities Operating Expense, Impairments	92,000,000	21,000,000
Interest Costs Incurred [Abstract]
Interest Costs Incurred	$ 8,000,000