Commitments and Contingencies - Contingencies Narrative (Details) (USD $)	3 Months Ended
	Mar. 31, 2015
Commitments And Contingencies Additional Narrative Information [Line Items]
Nuclear Insurance Financial Protection Pool Surcharge On Nuclear Incident Assessment	12730000000.00%
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 10,267,000,000
Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Total of U.S. licensed nuclear reactors	104
Nuclear financial protection pool value	375,000,000
Maximum liability per nuclear incident	13,600,000,000
Guarantor Obligations, Maximum Exposure, Undiscounted	7,365,000,000
Funds available for claim	13,200,000,000
Recovery of Direct Costs	3,200,000,000
Nuclear Insurance Premiums [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Maximum assessment mandated by Price-Anderson Act per nuclear reactor for a nuclear incident	2,700,000,000
Guarantor Obligations, Maximum Exposure, Undiscounted	3,014,000,000	[1]
Nuclear Insurance Premiums [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
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	19,000,000
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 3,014,000,000	[1]

[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.