Implications of Potential Early Plant Retirements Implications of Potential Early Plant Retirements (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross	$ 1,068	$ 1,024
Property, Plant and Equipment, Net	53,935	52,087
Nuclear Plant [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross	133
Nuclear Fuel, Net of Amortization	408
Property, Plant and Equipment, Net	1,350
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	71
Asset Retirement Obligation	(1,348)
Quad Cities [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross	48
Nuclear Fuel, Net of Amortization	205
Property, Plant and Equipment, Net	800
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	24
Asset Retirement Obligation	(450)
Clinton [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross	55
Nuclear Fuel, Net of Amortization	137
Property, Plant and Equipment, Net	465
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	24
Asset Retirement Obligation	(287)
Ginna [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross	30
Nuclear Fuel, Net of Amortization	66
Property, Plant and Equipment, Net	85
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	23
Asset Retirement Obligation	(611)
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross	860	847
Property, Plant and Equipment, Net	$ 23,766	$ 22,945