Commitments and Contingencies - Contingencies Narrative (Details) (USD $)	9 Months Ended									0 Months Ended
	Sep. 30, 2014	Sep. 30, 2014 Exelon Generation Co L L C [Member] reactor	Dec. 31, 2013 Exelon Generation Co L L C [Member]	Sep. 30, 2013 Exelon Generation Co L L C [Member]	Sep. 30, 2014 Nuclear Insurance Premiums [Member]		Sep. 30, 2014 Nuclear Insurance Premiums [Member] Exelon Generation Co L L C [Member]		Dec. 31, 2013 Sithe Guarantee [Member]	Jan. 31, 2005 Sithe Guarantee [Member] Exelon Generation Co L L C [Member]	Feb. 26, 2014 Sithe Guarantee [Member] Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Nuclear insurance liability limit per incident							$ 13,600,000,000
Required nuclear liability insurance per site		375,000,000
Total of U.S. licensed nuclear reactors		104
Nuclear financial protection pool value		13,200,000,000					19,000,000
Nuclear Insurance Financial Protection Pool Surcharge On Nuclear Incident Assessment	5.00%
Maximum assessment mandated by Price-Anderson Act per nuclear reactor for a nuclear incident							127,300,000
Maximum liability per nuclear incident				3,600,000,000			2,700,000,000
Cost of spent nuclear fuel disposal per kWh of net nuclear generation		0.001
Net Nuclear Fuel Disposal Fees		49,000,000	136,000,000
Acquisition of interest in subsidiary											50.00%
Sale of interest in subsidiary										100.00%
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 9,542,000,000	$ 6,136,000,000			$ 3,559,000,000	[1]	$ 3,559,000,000	[1]	$ 200,000,000

[1] Represents the maximum amount that Generation would be required to pay for retrospective premiums in the event of nuclear disaster at any domestic site, including CENG sites, under the Secondary Financial Protection pool as required under the Price-Anderson Act as well as the current aggregate annual retrospective premium obligation that could be imposed by NEIL. See the Nuclear Insurance section within this note for additional details on Generation’s nuclear insurance premiums.