Severance - Severance Liabilities (Details) $ in Millions	6 Months Ended
	Jun. 30, 2016 USD ($)
Restructuring Reserve [Roll Forward]
Beginning Balance	$ 35
Severance Charges Expense	(129)
Payments for Restructuring	(19)
Ending Balance	145
Exelon Generation Co L L C [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	23
Severance Charges Expense	(56)
Payments for Restructuring	(4)
Ending Balance	75
Commonwealth Edison Co [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	3
Severance Charges Expense	(1)
Payments for Restructuring	(1)
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
Payments for Restructuring	0
Ending Balance	1
Pepco Holdings LLC [Member]
Restructuring Reserve [Roll Forward]
Ending Balance	43
Potomac Electric Power Company [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	0
Severance Charges Expense	(1)
Payments for Restructuring	0
Ending Balance	1
Delmarva Power and Light Company [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	0
Severance Charges Expense	(1)
Payments for Restructuring	0
Ending Balance	1
Atlantic City Electric Company [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	0
Severance Charges Expense	0
Payments for Restructuring	0
Ending Balance	0
Successor [Member] | Pepco Holdings LLC [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	0
Severance Charges Expense	54
Payments for Restructuring	$ (11)