Severance - PHI Merger (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	$ 52
Exelon Generation Co L L C [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	2	$ 20
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	1
Exelon Generation Co L L C [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	10
Exelon Generation Co L L C [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	9
Commonwealth Edison Co [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	2
Commonwealth Edison Co [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	2
PECO Energy Co [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	1
PECO Energy Co [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	1
Baltimore Gas and Electric Company [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	1
Baltimore Gas and Electric Company [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	1
Pepco Holdings, LLC [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	37
Pepco Holdings, LLC [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	18
Potomac Electric Power Company [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	18
Delmarva Power and Light Company [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	11
Delmarva Power and Light Company [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	11
Atlantic City Electric Company [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	8
Atlantic City Electric Company [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	$ 8