Regulatory Matters Annual Electric Transmission Fillings (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
Commonwealth Edison Co [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 90.0
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ 94.0
Public Utilities, Approved Return on Equity, Percentage			11.50%
Public Utilities, Approved Equity Capital Structure, Percentage			8.47%	8.61%
Prior Year Revenue Adjustment			$ 4.0
Baltimore Gas and Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			12.0
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ 15.0
Public Utilities, Approved Return on Equity, Percentage			10.50%
Public Utilities, Approved Equity Capital Structure, Percentage			8.09%	8.46%
Prior Year Revenue Adjustment			$ 3.0
Potomac Electric Power Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			2.0
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ (23.0)
Public Utilities, Approved Return on Equity, Percentage		10.60%
Public Utilities, Approved Return on Equity, Percentage			10.50%
Public Utilities, Approved Equity Capital Structure, Percentage			7.88%	8.36%
Prior Year Revenue Adjustment		$ (10.0)
Current Year Revenue Adjustment			$ (15.0)
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, Requested Rate Increase (Decrease), Amended, Amount			$ (14.0)
Public Utilities, Approved Return on Equity, Percentage	9.70%
Public Utilities, Approved Return on Equity, Percentage			10.50%
Public Utilities, Requested Equity Capital Structure, Percentage			10.60%
Public Utilities, Approved Equity Capital Structure, Percentage			7.21%	7.80%
Prior Year Revenue Adjustment		(10.0)
Current Year Revenue Adjustment			$ (12.0)
Atlantic City Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			8.0
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ (6.0)
Public Utilities, Approved Return on Equity, Percentage			10.50%
Public Utilities, Approved Equity Capital Structure, Percentage			7.83%	8.51%
Prior Year Revenue Adjustment		$ (14.0)
Current Year Revenue Adjustment			$ 0.0