Severance - Cost Management Program-Related Severance (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 19	$ 18
Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	23
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	13	15
Exelon Generation Co L L C [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	18
Exelon Generation Co L L C [Member] | Cost Management Project [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		7
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	3	2
Commonwealth Edison Co [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	3
Commonwealth Edison Co [Member] | Cost Management Project [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		3
PECO Energy Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	1	0
PECO Energy Co [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	1
PECO Energy Co [Member] | Cost Management Project [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1
Baltimore Gas and Electric Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	1	$ 1
Baltimore Gas and Electric Company [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	1
Baltimore Gas and Electric Company [Member] | Cost Management Project [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 1

[1] 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 year ended December 31, 2016.

[2] 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.