Severance - Narrative (Details) $ in Millions		1 Months Ended	3 Months Ended	12 Months Ended
		Aug. 31, 2015	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
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
Exelon Generation Co L L C [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			$ 44
Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]			23
Restructuring and Related Cost, Expected Number of Positions Eliminated		500
Cost Management Project [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Number of Positions Eliminated		250
Cost Management Project [Member] | Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]			18
Restructuring and Related Cost, Expected Number of Positions Eliminated		250
Cost Management Project [Member] | Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				$ 7

[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.

[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 year ended December 31, 2016.