Impairment of Long-Lived Assets (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	May. 31, 2014	Oct. 31, 2000
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Tangible Asset Impairment Charges	$ 24
Estimated residual value of leased assets	639		$ 639		$ 685		$ 1,600
Capital Lease Net Investment In Direct Financing Leases Prepayments Received							$ 1,200
Proceeds From Lease Termination			0	$ 335
Operating and maintenance	2,042	$ 2,166	4,123	4,024
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						$ 151
Impaired Assets Fair Value						$ 65
Tangible Asset Impairment Charges		86
Operating and maintenance	$ 1,149	$ 1,255	$ 2,311	$ 2,194