Severance - Severance Liabilities (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($)
Restructuring Reserve [Roll Forward]
Beginning Balance	$ 35
Severance Charges Expense	71
Payments for Restructuring	4
Ending Balance	102
Exelon Generation Co L L C [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	23
Severance Charges Expense	7
Payments for Restructuring	3
Ending Balance	27
Commonwealth Edison Co [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	3
Severance Charges Expense	0
Payments for Restructuring	0
Ending Balance	3
PECO Energy Co [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	0
Severance Charges Expense	0
Payments for Restructuring	0
Ending Balance	0
Baltimore Gas and Electric Company [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	1
Severance Charges Expense	0
Ending Balance	1
Pepco Holdings, LLC [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	0
Severance Charges Expense	51
Payments for Restructuring	0
Ending Balance	51
Potomac Electric Power Company [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	0
Severance Charges Expense	0
Payments for Restructuring	0
Ending Balance	0
Delmarva Power and Light Company [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	0
Severance Charges Expense	0
Payments for Restructuring	0
Ending Balance	0
Atlantic City Electric Company [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	0
Severance Charges Expense	0
Payments for Restructuring	0
Ending Balance	$ 0