Severance Severance - Narrative (Details) $ in Millions		1 Months Ended		3 Months Ended		6 Months Ended
		Jun. 30, 2017 USD ($)	Aug. 31, 2015	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)		Jun. 30, 2016 USD ($)		Dec. 31, 2016 USD ($)
Restructuring Cost and Reserve [Line Items]
Severance Costs				$ 5	$ 2	$ 9		$ 4
Regulatory Assets		$ 11,238		11,238		11,238				$ 11,388
Merger Integration Costs [Member]
Restructuring Cost and Reserve [Line Items]
Regulatory Assets		32		32		32				25
Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Number of Positions Eliminated			500
Severance Costs						(1)	[1]	17	[2]
Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		(17)
Corporate, Non-Segment [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Number of Positions Eliminated			250
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[3]			1	1	4		3
Exelon Generation Co L L C [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Number of Positions Eliminated			250
Severance Costs						(1)	[1]	12	[2]
Exelon Generation Co L L C [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		(17)
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				1	1	1		2
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs								7
Potomac Electric Power Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[3]			1	0	1		0
Regulatory Assets		847		847		847				852
Potomac Electric Power Company [Member] | Merger Integration Costs [Member]
Restructuring Cost and Reserve [Line Items]
Regulatory Assets		12		12	9	12		9		11	[4]
Potomac Electric Power Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				1		1
Delmarva Power and Light Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[3]			1	0	1		0
Regulatory Assets		370		370		370				$ 348
Delmarva Power and Light Company [Member] | Merger Integration Costs [Member]
Restructuring Cost and Reserve [Line Items]
Regulatory Assets		$ 13		13	$ 3	13		$ 3
Delmarva Power and Light Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				$ 1		$ 1

[1] Amounts billed by BSC through intercompany allocations for the six months ended June 30, 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 six months ended June 30, 2016.

[3] The amounts above for Generation include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017, respectively, and $1 million and $2 million for the three and six months ended June 30, 2016, respectively. The amounts above for ComEd include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017, respectively, and less than $1 million and $1 million for the three and six months ended June 30, 2016, respectively. Amounts billed by PHISCO to Pepco, DPL and ACE were $1 million, each, for both three and six months ended June 30, 2017. Pepco, DPL and ACE did not have any ongoing severance plans for the three and six months ended June 30, 2016.

[4] As of June 30, 2017 and December 31, 2016, Pepco’s regulatory asset of $12 million and $11 million, respectively, represents previously incurred PHI acquisition costs authorized for recovery by the November 2016 Maryland distribution rate case order. As of June 30, 2017, DPL’s regulatory asset of $13 million represents previously incurred PHI acquisition costs, including $4 million authorized for recovery by the February 2017 Maryland distribution rate case order, $6 million authorized for recovery by the May 2017 Delaware electric distribution rate case order, and $3 million expected to be recovered in electric and gas distribution rates in the Delaware service territory. As of December 31, 2016, DPL's regulatory asset of $4 million represents previously incurred PHI acquisition costs expected to be recovered in distribution rates in the Maryland service territory.