Property, Plant and Equipment Annual Depreciation Provisions as Percentage of Average Service Life (Details)	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.73%		2.83%	2.93%
Electric—generation
Property, Plant and Equipment [Line Items]
Annual depreciation rate	5.94%	[1]	3.47%	3.50%
Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.17%		2.17%	2.13%
Common—electric and gas
Property, Plant and Equipment [Line Items]
Annual depreciation rate	7.41%		7.79%	7.32%
PECO Energy Co [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.32%		2.39%	2.55%
PECO Energy Co [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Annual depreciation rate	1.82%		1.87%	1.84%
PECO Energy Co [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Annual depreciation rate	5.11%		5.16%	5.16%
Baltimore Gas and Electric Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.56%		2.62%	2.96%
Baltimore Gas and Electric Company [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.45%		2.50%	2.47%
Baltimore Gas and Electric Company [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Annual depreciation rate	9.45%		10.35%	9.49%
Pepco Holdings LLC [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.52%		2.48%	2.42%
Pepco Holdings LLC [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.57%		2.55%	2.48%
Pepco Holdings LLC [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Annual depreciation rate	8.12%		5.19%	4.55%
Delmarva Power and Light Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.49%		2.44%	2.41%
Delmarva Power and Light Company [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.57%		2.55%	2.48%
Delmarva Power and Light Company [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Annual depreciation rate	4.99%		4.24%	4.08%

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