Commitments and Contingencies - Schedule of Government Agreement Settlements (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015
Schedule of Government Agreements [Line Items]
Nontrade Receivables, Current		$ 109	$ 76
Nontrade Receivables, Noncurrent		15	14
Accounts Payable, Other, Current		(13)	$ (5)
Exelon Generation Co L L C [Member]
Schedule of Government Agreements [Line Items]
Spent Nuclear Fuel Storage Reimbursement		1,038
Spent Nuclear Fuel Storage Reimbursement Net Co Owners		$ 887
Department of Energy [Member] | Exelon Generation Co L L C [Member]
Schedule of Government Agreements [Line Items]
Spent Nuclear Fuel Storage Reimbursement	$ 53
Spent Nuclear Fuel Storage Reimbursement Net Co Owners	$ 49