Commitments and Contingencies Commitments and Contingencies - Schedule of Minimum Future Operating Lease Payments (Details) - USD ($) $ in Millions		Dec. 31, 2018		Nov. 30, 2016
Operating Leases Future Minimum Payments Due [Line Items]
2018	[1],[2]	$ 140
2019	[1],[2]	149
2020	[1],[2]	143
2021	[1],[2]	126
2022	[1],[2]	97
Remaining Years	[1],[2]	723
Total minimum future lease payments	[1],[2]	1,378
Exelon Generation Co L L C [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2018	[1],[2]	33
2019	[1],[2]	46
2020	[1],[2]	46
2021	[1],[2]	47
2022	[1],[2]	46
Remaining Years	[1],[2]	545
Total minimum future lease payments	[1],[2]	763
Commonwealth Edison Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2018	[2],[3]	7
2019	[2],[3]	5
2020	[2],[3]	4
2021	[2],[3]	4
2022	[2],[3]	3
Remaining Years	[2],[3]	0
Total minimum future lease payments	[2],[3]	23
Commonwealth Edison Co [Member] | Real Estate Leases and Railroad Licenses [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total minimum future lease payments		3
PECO Energy Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2018	[2],[3]	5
2019	[2],[3]	5
2020	[2],[3]	5
2021	[2],[3]	5
2022	[2],[3]	5
Remaining Years	[2],[3]	0
Total minimum future lease payments	[2],[3]	25
PECO Energy Co [Member] | Real Estate Leases and Railroad Licenses [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total minimum future lease payments		5
Baltimore Gas and Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2018		35	[2],[3],[4],[5]	$ 26
2019		35	[2],[3],[4],[5]	28
2020		33	[2],[3],[4],[5]	28
2021		18	[2],[3],[4],[5]	$ 14
2022	[2],[3],[4],[5]	3
Remaining Years	[2],[3],[4],[5]	19
Total minimum future lease payments	[2],[3],[4],[5]	143
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
Pepco Holdings LLC [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2018	[2]	48
2019	[2]	46
2020	[2]	43
2021	[2]	42
2022	[2]	39
Remaining Years	[2]	159
Total minimum future lease payments	[2]	377
Potomac Electric Power Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2018	[2]	11
2019	[2]	10
2020	[2]	9
2021	[2]	8
2022	[2]	8
Remaining Years	[2]	40
Total minimum future lease payments	[2]	86
Delmarva Power & Light Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2018	[2],[3]	14
2019	[2],[3]	13
2020	[2],[3]	12
2021	[2],[3]	12
2022	[2],[3]	10
Remaining Years	[2],[3]	35
Total minimum future lease payments	[2],[3]	96
Delmarva Power & Light Company [Member] | Real Estate Leases and Railroad Licenses [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total minimum future lease payments		1
Atlantic City Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2018	[2]	7
2019	[2]	6
2020	[2]	5
2021	[2]	5
2022	[2]	4
Remaining Years	[2]	5
Total minimum future lease payments	[2]	$ 32

[1] )Excludes Generation’s contingent operating lease payments associated with contracted generation agreement

[2] )Includes amounts related to shared use land arrangement

[3] )Amounts related to certain real estate leases and railroad licenses effectively have indefinite payment periods. As a result, ComEd, PECO, BGE and DPL have excluded these payments from the remaining years as such amounts would not be meaningful. ComEd's, PECO’s, BGE’s and DPL's average annual obligation for these arrangements, included in each of the years 2019 - 2023, was $3 million, $5 million, $1 million and $1 million respectivel

[4] )The BGE column above includes minimum future lease payments associated with a 6-year lease for the Baltimore City conduit system that became effective during the fourth quarter of 2016. BGE's total commitments under the lease agreement are $26 million, $28 million, $28 million and $14 million related to years 2019 - 2022 , respectivel

[5] )The BGE column above includes minimum future lease payments associated with a 6-year lease for the Baltimore City conduit system that became effective during the fourth quarter of 2016. BGE's total commitments under the lease agreement are $26 million, $28 million, $28 million and $14 million related to years 2019 - 2022 , respectivel