Regulatory Matters Annual Electric Distribution Filings (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	6 Months Ended
	Aug. 31, 2014	Jun. 30, 2016	Jun. 30, 2016	Jun. 30, 2015
Potomac Electric Power Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 2.0
Rate Of Return On Common Equity In Federal Energy Regulatory Committee Complaint			10.50%
Public Utilities, Approved Equity Capital Structure, Percentage			7.88%	8.36%
Delmarva Power and Light Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 62.8	$ 8.0
Public Utilities, Approved Rate Increase (Decrease), Amount	$ 15.0
Rate Of Return On Common Equity In Federal Energy Regulatory Committee Complaint			10.50%
Public Utilities, Approved Equity Capital Structure, Percentage			7.21%	7.80%
Atlantic City Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 8.0
Rate Of Return On Common Equity In Federal Energy Regulatory Committee Complaint			10.50%
Public Utilities, Approved Equity Capital Structure, Percentage			7.83%	8.51%
Baltimore Gas and Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 12.0
Rate Of Return On Common Equity In Federal Energy Regulatory Committee Complaint			10.50%
Public Utilities, Approved Equity Capital Structure, Percentage			8.09%	8.46%