Severance - Ongoing Severance Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	$ 1	$ 4	$ 21	$ 6
Exelon Generation Co L L C [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	(1)	2	17	4
Commonwealth Edison Co [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	0	0	0	0
PECO Energy Co [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	0	0	0	0
Baltimore Gas and Electric Company [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	$ 0	$ 0	$ 0	$ 0