Nuclear Decommissioning (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended		9 Months Ended			9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2014 Exelon Generation Co L L C [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member]	Dec. 31, 2012 Exelon Generation Co L L C [Member]	Sep. 30, 2014 Nuclear Plant [Member] Exelon Generation Co L L C [Member]	Sep. 30, 2013 Limerick and Three Mile Island Nuclear Units [Member] Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Period Increase (Decrease)				$ 1,800			$ 17	$ 51
Other Income	16
Nuclear Decommissioning Annual Recovery Current		24
Decommissioning Shortfall				50
Decommissioning Shortfall Percentage				5.00%
Half Of Non Decommissioning Withdraw		50.00%
Decommissioning Fund Investments	10,349	10,349	8,071	10,349	8,071
Decommissioning Liability, Noncurrent	260	260	305	260	305		85
Additional NRC Funding Assurance Parent Guarantees						$ 115