Severance Severance - PHI Merger (Details) - PHI Merger [Member] $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Restructuring Cost and Reserve [Line Items]
Severance Costs	$ 57
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	9
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	2
PECO Energy Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	1
Baltimore Gas and Electric Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	1
Pepco Holdings LLC [Member] | Successor [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	44
Potomac Electric Power Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	21
Delmarva Power & Light Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	13
Atlantic City Electric Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	$ 10