Commitments and Contingencies - Schedule of Minimum Future Operating Lease Payments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)
Operating Leases Future Minimum Payments Due [Line Items]
2015	$ 133
2016	109
2017	86
2018	74
2019	70
Remaining years	702
Total minimum future lease payments	1,174	[1]
Exelon Generation Co L L C [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2015	86	[2]
2016	69	[2]
2017	57	[2]
2018	45	[2]
2019	44	[2]
Remaining years	655	[2]
Total minimum future lease payments	956	[1],[2]
Exelon Generation Co L L C [Member] | Baltimore Headquarters [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2016	10
2017	11
2018	13
2019	14
Remaining years	271
Commonwealth Edison Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2015	14	[3]
2016	9	[3]
2017	5	[3]
2018	5	[3]
2019	3	[3]
Remaining years	1	[3]
Total minimum future lease payments	37	[3]
Commonwealth Edison Co [Member] | Real Estate Leases and Railroad Licenses [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total minimum future lease payments	2
PECO Energy Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2015	3	[3]
2016	3	[3]
2017	2	[3]
2018	2	[3]
2019	2	[3]
Remaining years	0	[3]
Total minimum future lease payments	12	[3]
PECO Energy Co [Member] | Real Estate Leases and Railroad Licenses [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total minimum future lease payments	3
Baltimore Gas and Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2015	12	[3],[4]
2016	10	[3],[4]
2017	9	[3],[4]
2018	8	[3],[4]
2019	7	[3],[4]
Remaining years	19	[3],[4]
Total minimum future lease payments	$ 65	[3],[4]
Baltimore Gas and Electric Company [Member] | Baltimore Headquarters [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Term of lease	20 years
Baltimore Gas and Electric Company [Member] | Real Estate Leases and Railroad Licenses [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total minimum future lease payments	$ 1

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[2] The Generation column above includes minimum future lease payments associated with a 20-year lease agreement for the Baltimore headquarters that became effective during the second quarter of 2015. Generation’s total commitments under the lease agreement are $4 million, $10 million, $11 million, $13 million, $14 million, and $271 million related to years 2016, 2017, 2018, 2019, 2020 and thereafter, respectively.

[3] Amounts related to certain real estate leases and railroad licenses effectively have indefinite payment periods. As a result, ComEd, PECO and BGE have excluded these payments from the remaining years, as such amounts would not be meaningful. ComEd’s, PECO’s, and BGE’s annual obligation for these arrangements, included in each of the years 2016—2020, was $2 million, $3 million, and $1 million respectively.

[4] Includes all future lease payments on a 99 year real estate lease that expires in 2106.