Severance - Ongoing Severance Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	$ 8	$ (3)	$ 12	$ 18
Regulatory Assets	11,432		11,432		$ 6,824
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
Commonwealth Edison Co [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs	0	$ 0	1
Regulatory Assets	1,192		1,192		1,113
Commonwealth Edison Co [Member] | Corporate, Non-Segment [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance Costs			1
PECO Energy Co [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Regulatory Assets	1,688		1,688		1,617
Baltimore Gas and Electric Company [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Regulatory Assets	722		722		781
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
Potomac Electric Power Company [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Regulatory Assets	798		798		801
Delmarva Power and Light Company [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Regulatory Assets	359		359		371
Atlantic City Electric Company [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Regulatory Assets	$ 501		$ 501		$ 512