Severance - PHI Merger (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	$ 2	$ 1	$ 4	$ 21
PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	2		55
Exelon Generation Co L L C [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	1	1	3	21
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	1	2	2	4
Exelon Generation Co L L C [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	(1)		9
Exelon Generation Co L L C [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	(1)		8
Commonwealth Edison Co [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	1	$ 0	1	$ 0
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	(1)		2
Commonwealth Edison Co [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	(1)		2
PECO Energy Co [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	0		1
PECO Energy Co [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	1		1
Baltimore Gas and Electric Company [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	0		1
Baltimore Gas and Electric Company [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	1		1
Pepco Holdings LLC [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	4		42
Pepco Holdings LLC [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	2		19
Potomac Electric Power Company [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	2		20
Delmarva Power and Light Company [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	1		12
Delmarva Power and Light Company [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	1		11
Atlantic City Electric Company [Member] | PHI Merger [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	1		10
Atlantic City Electric Company [Member] | PHI Merger [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	$ 1		$ 10