Severance Severance - Cost Management Program-Related (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 8	$ 4
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	2	3
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	1	1
PECO Energy Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	0	0
Baltimore Gas and Electric Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	$ 1	$ 0

[1] The amounts above for Generation, ComEd, PECO, BGE, and PHI include immaterial amounts billed by BSC the three months ended March 31, 2018 and 2017. Pepco, DPL and ACE include immaterial amounts billed by PHISCO for the three months ended March 31, 2018 and 2017.