Severance - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Restructuring Cost and Reserve [Line Items]
Severance Costs	$ 2	$ 1	$ 4	$ 21
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	1	1	3	21
Exelon Generation Co L L C [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	46
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	1	$ 2	$ 2	$ 4
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	$ 3