Impairment of Long-Lived Assets (Details) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Sep. 30, 2000
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Capital Leases, Net Investment in Direct Financing Leases, Unguaranteed Residual Values of Leased Property	$ 685,000,000				$ 685,000,000		$ 1,465,000,000	$ 1,600,000,000
Less: unearned income	(332,000,000)				(332,000,000)		(767,000,000)
Net investment in long-term leases	353,000,000				353,000,000		698,000,000
Carring Amount Of Long Lived Assets To Be Written Down	151,000,000				151,000,000
ImpairedAssetsFairValue	65,000,000				65,000,000
Other Cost and Expense, Operating	2,166,000,000	1,000,000	1,892,000,000		4,024,000,000	3,656,000,000
CapitalLeasesNetInvestmentInDirectFinancingLeasesWriteoff	336,000,000				336,000,000
ProceedsFromLeaseTermination					335,000,000
Tangible Asset Impairment Charges					86,000,000
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]
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Carring Amount Of Long Lived Assets To Be Written Down	151,000,000				151,000,000
ImpairedAssetsFairValue	65,000,000				65,000,000
Other Cost and Expense, Operating	1,255,000,000		1,041,000,000		2,194,000,000	2,007,000,000
Tangible Asset Impairment Charges					86,000,000
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
Commonwealth Edison Co [Member]
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Other Cost and Expense, Operating	316,000,000		319,000,000		603,000,000	611,000,000
PECO Energy Co [Member]
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Other Cost and Expense, Operating	160,000,000		155,000,000		416,000,000	319,000,000
Baltimore Gas and Electric Company [Member]
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Other Cost and Expense, Operating	$ 163,000,000		$ 139,000,000		$ 326,000,000	$ 266,000,000