Leases Lessee 2018 Schedule of Minimum Future Operating Lease Payments (Details) $ in Millions	Dec. 31, 2018 USD ($)
Operating Leases Future Minimum Payments Due [Line Items]
2019	$ 140	[1],[2]
2020	149	[1],[2]
2021	143	[1],[2]
2022	126	[1],[2]
2023	97	[1],[2]
Remaining Years	723	[1],[2]
Total Minimum Future Operating Lease Payments Due	1,378	[1],[2]
Exelon Generation Co L L C [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	33	[1],[2]
2020	46	[1],[2]
2021	46	[1],[2]
2022	47	[1],[2]
2023	46	[1],[2]
Remaining Years	545	[1],[2]
Total Minimum Future Operating Lease Payments Due	763	[1],[2]
Commonwealth Edison Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	7	[2],[3]
2020	5	[2],[3]
2021	4	[2],[3]
2022	4	[2],[3]
2023	3	[2],[3]
Remaining Years	0	[2],[3]
Total Minimum Future Operating Lease Payments Due	23	[2],[3]
PECO Energy Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	5	[2],[3]
2020	5	[2],[3]
2021	5	[2],[3]
2022	5	[2],[3]
2023	5	[2],[3]
Remaining Years	0	[2],[3]
Total Minimum Future Operating Lease Payments Due	25	[2],[3]
Baltimore Gas and Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	35	[2],[3],[4],[5]
2020	35	[2],[3],[4],[5]
2021	33	[2],[3],[4],[5]
2022	18	[2],[3],[4],[5]
2023	3	[2],[3],[4],[5]
Remaining Years	19	[2],[3],[4],[5]
Total Minimum Future Operating Lease Payments Due	143	[2],[3],[4],[5]
Pepco Holdings LLC [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	48	[2]
2020	46	[2]
2021	43	[2]
2022	42	[2]
2023	39	[2]
Remaining Years	159	[2]
Total Minimum Future Operating Lease Payments Due	377	[2]
Potomac Electric Power Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	11	[2]
2020	10	[2]
2021	9	[2]
2022	8	[2]
2023	8	[2]
Remaining Years	40	[2]
Total Minimum Future Operating Lease Payments Due	86	[2]
Delmarva Power and Light Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	14	[2],[3]
2020	13	[2],[3]
2021	12	[2],[3]
2022	12	[2],[3]
2023	10	[2],[3]
Remaining Years	35	[2],[3]
Total Minimum Future Operating Lease Payments Due	96	[2],[3]
Atlantic City Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	7	[2]
2020	6	[2]
2021	5	[2]
2022	5	[2]
2023	4	[2]
Remaining Years	5	[2]
Total Minimum Future Operating Lease Payments Due	32	[2]
Real Estate Leases and Railroad Licenses [Member] | Commonwealth Edison Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total Minimum Future Operating Lease Payments Due	3
Real Estate Leases and Railroad Licenses [Member] | PECO Energy Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total Minimum Future Operating Lease Payments Due	5
Real Estate Leases and Railroad Licenses [Member] | Baltimore Gas and Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total Minimum Future Operating Lease Payments Due	1
Real Estate Leases and Railroad Licenses [Member] | Delmarva Power and Light Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total Minimum Future Operating Lease Payments Due	1
Electrical Conduit System [Member] | Baltimore Gas and Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	26
2020	28
2021	28
2022	$ 14

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

[2] Includes amounts related to shared use land arrangements.

[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 respectively. Also includes amounts related to shared use land arrangements.

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

[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, respectively.