Commitments and Contingencies - Schedule of Government Agreement Settlements (Details) - USD ($) $ in Millions		9 Months Ended	12 Months Ended
		Dec. 31, 2014	Dec. 31, 2015
Schedule of Government Agreements [Line Items]
Nontrade Receivables, Current		$ 82	$ 76
Nontrade Receivables, Noncurrent		7	14
Accounts Payable, Other, Current		(5)	(5)
Exelon Generation Co L L C [Member]
Schedule of Government Agreements [Line Items]
Spent Nuclear Fuel Storage Reimbursement			945
Spent Nuclear Fuel Storage Reimbursement Net Co Owners			$ 804
Department of Energy [Member] | Exelon Generation Co L L C [Member]
Schedule of Government Agreements [Line Items]
Spent Nuclear Fuel Storage Reimbursement	[1]	53
Spent Nuclear Fuel Storage Reimbursement Net Co Owners	[1],[2]	$ 49

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