Property, Plant and Equipment - Narrative (Details)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Electric Generation Equipment [Member]
Property, Plant and Equipment [Line Items]
Annual depreciation rate	3.50%	3.35%	3.15%
Exelon Generation Co L L C [Member] | Electric Generation Equipment [Member]
Property, Plant and Equipment [Line Items]
Annual depreciation rate	3.50%	3.35%	3.15%
Commonwealth Edison Co [Member]
Property, Plant and Equipment [Line Items]
Annual depreciation rate	3.05%	2.97%	2.79%