Severance - PHI Merger (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	$ 8	$ (3)	$ 12	$ 18
PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs			55
Exelon Generation Co L L C [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	7	(3)	10	$ 17
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	1		2
Exelon Generation Co L L C [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs			9
Exelon Generation Co L L C [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs			8
Commonwealth Edison Co [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	0	$ 0	1
Commonwealth Edison Co [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs			1
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]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	$ 1		1
Pepco Holdings LLC [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			42
Potomac Electric Power Company [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs			20
Potomac Electric Power Company [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs			19
Delmarva Power and Light Company [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs			12
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			10
Atlantic City Electric Company [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs			$ 10