Property, Plant and Equipment Property, Plant and Equipment- Annual Depreciation Provisions as Percentage of Average Service Life (Details)	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.73%		2.75%		2.73%
Electric—generation
Property, Plant and Equipment [Line Items]
Annual depreciation rate	5.37%	[1]	4.36%	[1]	5.94%
Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.07%		2.10%		2.17%
Common—electric and gas
Property, Plant and Equipment [Line Items]
Annual depreciation rate	6.98%		7.05%		7.41%
PECO Energy Co [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.35%		2.37%		2.32%
PECO Energy Co [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Annual depreciation rate	1.90%		1.89%		1.82%
PECO Energy Co [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Annual depreciation rate	5.44%		5.47%		5.11%
Baltimore Gas and Electric Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.61%		2.58%		2.56%
Baltimore Gas and Electric Company [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.36%		2.33%		2.45%
Baltimore Gas and Electric Company [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Annual depreciation rate	8.50%		8.64%		9.45%
Pepco Holdings LLC [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.61%		2.63%		2.52%
Pepco Holdings LLC [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Annual depreciation rate	1.59%		2.07%		2.57%
Pepco Holdings LLC [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Annual depreciation rate	6.30%		6.50%		8.12%
Delmarva Power & Light Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.77%		2.75%		2.49%
Delmarva Power & Light Company [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Annual depreciation rate	1.59%		2.07%		2.57%
Delmarva Power & Light Company [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Annual depreciation rate	3.70%		4.14%		4.99%

[1] See Note 8 — Early Plant Retirements for additional information on the accelerated net depreciation and amortization of Clinton, Quad Cities, Oyster Creek and TMI.