Lessor - Operating Lease, Payments, Fiscal Year Maturity (Details) $ in Millions	Dec. 31, 2019 USD ($)
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	$ 51
2020	51
2021	50
2022	49
2023	48
Remaining years	265
Total Lessor, Operating Lease, Payments to be Received	514
Exelon Generation Co L L C [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	46
2020	45
2021	45
2022	44
2023	44
Remaining years	226
Total Lessor, Operating Lease, Payments to be Received	450
Commonwealth Edison Co [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	0
2020	0
2021	0
2022	0
2023	0
Remaining years	1
Total Lessor, Operating Lease, Payments to be Received	1
PECO Energy Co [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	0
2020	0
2021	0
2022	0
2023	0
Remaining years	3
Total Lessor, Operating Lease, Payments to be Received	3
Baltimore Gas and Electric Company [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	0
2020	0
2021	0
2022	0
2023	0
Remaining years	1
Total Lessor, Operating Lease, Payments to be Received	1
Pepco Holdings LLC [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	4
2020	4
2021	4
2022	5
2023	4
Remaining years	34
Total Lessor, Operating Lease, Payments to be Received	55
Potomac Electric Power Company [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	0
2020	1
2021	0
2022	0
2023	0
Remaining years	0
Total Lessor, Operating Lease, Payments to be Received	1
Delmarva Power & Light Company [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	3
2020	3
2021	3
2022	4
2023	4
Remaining years	34
Total Lessor, Operating Lease, Payments to be Received	51
Atlantic City Electric Company [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	0
2020	0
2021	0
2022	0
2023	0
Remaining years	0
Total Lessor, Operating Lease, Payments to be Received	$ 0