Severance Severance - Cost Management Program-Related (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017		Mar. 31, 2016
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ (4)		$ (2)
Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		(1)	[1]	(17)	[2]
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[3]	(3)		(2)
Exelon Generation Co L L C [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		(1)	[1]	(12)	[2]
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]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[3]	(1)		0
Commonwealth Edison Co [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		0	[1]	(3)	[2]
Commonwealth Edison Co [Member] | Corporate, Non-Segment [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				(3)
PECO Energy Co [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		0	[1]	(1)	[2]
PECO Energy Co [Member] | Corporate, Non-Segment [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				(1)
Baltimore Gas and Electric Company [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 0	[1]	(1)	[2]
Baltimore Gas and Electric Company [Member] | Corporate, Non-Segment [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				$ (1)

[1] (a)Amounts billed by BSC through intercompany allocations for the three months ended March 31, 2017 were immaterial.

[2] The amounts above for Generation, ComEd, PECO and BGE include $7 million, $3 million, $1 million and $1 million, respectively, for amounts billed by BSC through intercompany allocations for the three months ended March 31, 2016.

[3] 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.