Severance - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Restructuring Cost and Reserve [Line Items]
Severance Costs	$ 8	$ (3)	$ 12	$ 18
Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	(2)		44
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	7	$ (3)	10	$ 17
Exelon Generation Co L L C [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	(2)		44
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	1		$ 2
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	$ 2