Property, Plant and Equipment - Narrative (Details)	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Electric—generation
Property, Plant and Equipment [Line Items]
Annual depreciation rate	5.94%	[1]	3.47%	3.50%
Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.73%		2.83%	2.93%
Exelon Generation Co L L C [Member] | Electric—generation
Property, Plant and Equipment [Line Items]
Annual depreciation rate	5.94%		3.47%	3.50%
Commonwealth Edison Co [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	3.03%		3.03%	3.05%
Potomac Electric Power Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.17%		2.13%	2.10%
Atlantic City Electric Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.45%		2.46%	2.48%

[1] See Note 9—Early Nuclear Plant Retirements for additional information on the accelerated net depreciation and amortization of Clinton and Quad Cities.