Nuclear Decommissioning - Rollforward of Nuclear Decommissioning ARO (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]	$ 333	$ 291
Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]	332	$ 291
Current portion of ARO				$ 7
Exelon Generation Co L L C [Member] | Oyster Creek [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Revision of Estimate		60
Exelon Generation Co L L C [Member] | Clinton And Quad Cities [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Revision of Estimate		384
Exelon Generation Co L L C [Member] | Nuclear Decommissioning [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Nuclear Decommissioning ARO, Beginning Balance	[2]	8,246
Asset Retirement Obligation, Accretion Expense		325
Asset Retirement Obligation, Liabilities Settled		(6)
Asset Retirement Obligation, Period Increase (Decrease)		763
Asset Retirement Obligation, Revision of Estimate		444
Nuclear Decommissioning ARO, Ending Balance	[2]	9,009
Current portion of ARO		$ 44

[1] Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income

[2] Includes $44 million and $7 million for the current portion of the ARO at September 30, 2016 and December 31, 2015, respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets.