Severance - PHI Merger (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 4	$ 2
PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		52
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	3	2
Exelon Generation Co L L C [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		10
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] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			9
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	$ 1	0
Commonwealth Edison Co [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		2
Commonwealth Edison Co [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			2
PECO Energy Co [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		1
PECO Energy Co [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			1
Baltimore Gas and Electric Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		1
Baltimore Gas and Electric Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			1
Pepco Holdings LLC [Member] | Successor [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		37
Potomac Electric Power Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		18
Potomac Electric Power Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			18
Delmarva Power and Light Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		11
Delmarva Power and Light Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			11
Atlantic City Electric Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		8
Atlantic City Electric Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			$ 8

[1] (a)The amounts above for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE include $9 million, $2 million, $1 million, $1 million, $18 million, $11 million and $8 million, respectively, for amounts billed by BSC and/or PHISCO through intercompany allocations for the three months ended March 31, 2016.

[2] he amounts above for Generation include $1 million for amounts billed by BSC through intercompany allocations for both the three months ended March 31, 2017 and 2016. Amounts billed by BSC to ComEd were immaterial.