Severance Severance - Cost Management Program-Related (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	$ 17
PECO Energy Co [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	1
PECO Energy Co [Member] | Corporate, Non-Segment [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	1
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	2	$ 20
Exelon Generation Co L L C [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	12
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	1
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	7
Commonwealth Edison Co [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	3
Commonwealth Edison Co [Member] | Corporate, Non-Segment [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	3
Baltimore Gas and Electric Company [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	1
Baltimore Gas and Electric Company [Member] | Corporate, Non-Segment [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	$ 1