Commitments and Contingencies - Schedule of Government Agreement Settlements (Details) (Department of Energy [Member], Exelon Generation Co L L C [Member], USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended
	Dec. 31, 2014		Dec. 31, 2014		Dec. 31, 2013
Department of Energy [Member] | Exelon Generation Co L L C [Member]
Schedule of Government Agreements [Line Items]
Spent Nuclear Fuel Storage Reimbursement	$ 33	[1]	$ 836	[1]
Spent Nuclear Fuel Storage Reimbursement Net Co Owners	30	[1],[2]	702	[1],[2]
DOE Receivable - Current	82	[3]	82	[3]	71	[3]
DOE Receivable - Noncurrent	7	[4]	7	[4]	0	[4]
Amounts owed to co-owners	$ (5)	[3],[5]	$ (5)	[3],[5]	$ (18)	[3],[5]

[1] Includes $33 million and $30 million, respectively, for amounts received since April 1, 2014, for costs incurred under the CENG DOE Settlement Agreements prior to the consolidation of CENG.

[2] Total after considering amounts due to co-owners of certain nuclear stations and to the former owner of Oyster Creek.

[3] Recorded in Accounts receivable, other.

[4] Recorded in Deferred debits and other assets, other

[5] Represents amounts owed to the co-owners of Peach Bottom, Quad Cities, and Nine Mile Point Unit 2 generating facilities.