Severance - Ongoing Severance Plans (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Severance Costs				$ 19	$ 18
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			13	15
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			3	2
PECO Energy Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			1	0
Baltimore Gas and Electric Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			$ 1	1
Pepco Holdings LLC [Member] | Successor [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		$ 1
Pepco Holdings LLC [Member] | Predecessor [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	$ 0			$ 0

[1] The amounts above for Generation, ComEd, PECO, BGE and PHI include immaterial amounts billed by BSC for the years ended December 31, 2016 and 2015.