Leases Lessee - Future Minimum Operating Lease Maturity Payments (Details) $ in Millions	Sep. 30, 2019 USD ($)
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	$ 65
2020	289
2021	246
2022	179
2023	148
Remaining Years	1,123
Total	2,050
Interest	453
Total Operating Lease Liabilities	1,597
Exelon Generation Co L L C [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	50
2020	203
2021	162
2022	113
2023	100
Remaining Years	837
Total	1,465
Interest	346
Total Operating Lease Liabilities	1,119
Commonwealth Edison Co [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	1
2020	3
2021	3
2022	2
2023	1
Remaining Years	2
Total	12
Interest	1
Total Operating Lease Liabilities	11
PECO Energy Co [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	0
2020	1
2021	0
2022	0
2023	0
Remaining Years	0
Total	1
Interest	0
Total Operating Lease Liabilities	1
Baltimore Gas and Electric Company [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	1
2020	34
2021	31
2022	16
2023	0
Remaining Years	19
Total	101
Interest	19
Total Operating Lease Liabilities	82
Pepco Holdings LLC [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	11
2020	45
2021	43
2022	42
2023	41
Remaining Years	197
Total	379
Interest	65
Total Operating Lease Liabilities	314
Potomac Electric Power Company [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	3
2020	10
2021	9
2022	9
2023	8
Remaining Years	43
Total	82
Interest	14
Total Operating Lease Liabilities	68
Delmarva Power and Light Company [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	2
2020	13
2021	12
2022	12
2023	11
Remaining Years	53
Total	103
Interest	18
Total Operating Lease Liabilities	85
Atlantic City Electric Company [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	2
2020	5
2021	5
2022	4
2023	4
Remaining Years	6
Total	26
Interest	2
Total Operating Lease Liabilities	$ 24