Implications of Potential Early Plant Retirements Implications of Potential Early Plant Retirements (Details) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross		$ 1,074	$ 1,024
Property, Plant and Equipment, Net		55,814	52,087
Nuclear Plant [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross		135
Nuclear Fuel, Net of Amortization		373
Property, Plant and Equipment, Net		1,720
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress		60
Asset Retirement Obligation		(1,729)
Quad Cities [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross		49
Nuclear Fuel, Net of Amortization		186
Property, Plant and Equipment, Net		1,027
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress		29
Asset Retirement Obligation		(696)
Clinton [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross		56
Nuclear Fuel, Net of Amortization		122
Property, Plant and Equipment, Net		582
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress		8
Asset Retirement Obligation		(396)
Ginna [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross		30
Nuclear Fuel, Net of Amortization		65
Property, Plant and Equipment, Net		111
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress		23
Asset Retirement Obligation		(637)
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross		863	847
Property, Plant and Equipment, Net		24,982	22,945
Exelon Generation Co L L C [Member] | Nuclear Plant [Member]
Property, Plant and Equipment [Line Items]
Asset Retirement Obligation	[1]	$ (8,073)	$ (6,961)

[1] Includes $7 million and $8 million as the current portion of the ARO at September 30, 2015 and December 31, 2014 respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets.