Severance - Ongoing Severance Plans (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
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
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