Impairment of Long-Lived Assets (Details) (USD $)	3 Months Ended					9 Months Ended				3 Months Ended				6 Months Ended	9 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Jun. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Oct. 31, 2000	Sep. 30, 2014 Exelon Generation Co L L C [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member]	Mar. 31, 2013 Exelon Generation Co L L C [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member]	Sep. 30, 2014 Exelon Generation Co L L C [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member]	May 31, 2014 Exelon Generation Co L L C [Member]
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Carrying Amount Of Long Lived Assets To Be Written Down												$ 75,000,000				$ 75,000,000	$ 151,000,000
Impaired Assets Fair Value												32,000,000				32,000,000	65,000,000
Tangible Asset Impairment Charges		24,000,000			14,000,000						86,000,000	39,000,000
Utilities Operating Expense, Impairments													21,000,000	92,000,000
Interest Costs Incurred														8,000,000
Estimated residual value of leased assets	685,000,000					685,000,000		1,465,000,000	1,600,000,000
Capital Lease Net Investment In Direct Financing Leases Prepayments Received									1,200,000,000
Proceeds From Lease Termination			335,000,000			335,000,000	0
Capital Leases Net Investment In Direct Financing Leases Writeoff			336,000,000
Operating and maintenance	1,982,000,000		1,000,000	1,735,000,000		6,005,000,000	5,391,000,000			1,114,000,000		936,000,000			3,308,000,000	2,943,000,000
Impairment of Long-Lived Assets to be Disposed of															$ 50,000,000