Leases Lessee Future Minimum Operating Lease Maturity Payments (Details) $ in Millions	Jun. 30, 2019 USD ($)
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	$ 149
2020	291
2021	246
2022	177
2023	141
Remaining Years	1,051
Total	2,055
Interest	452
Total Operating Lease Liabilities	1,603
Exelon Generation Co L L C [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	104
2020	202
2021	161
2022	112
2023	99
Remaining Years	834
Total	1,512
Interest	358
Total Operating Lease Liabilities	1,154
Commonwealth Edison Co [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	2
2020	3
2021	3
2022	2
2023	1
Remaining Years	2
Total	13
Interest	1
Total Operating Lease Liabilities	12
PECO Energy Co [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	1
2020	1
2021	0
2022	0
2023	0
Remaining Years	0
Total	2
Interest	0
Total Operating Lease Liabilities	2
Baltimore Gas and Electric Company [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	17
2020	34
2021	31
2022	16
2023	0
Remaining Years	19
Total	117
Interest	20
Total Operating Lease Liabilities	97
Pepco Holdings LLC [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	23
2020	44
2021	42
2022	41
2023	39
Remaining Years	196
Total	385
Interest	69
Total Operating Lease Liabilities	316
Potomac Electric Power Company [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	6
2020	9
2021	9
2022	8
2023	8
Remaining Years	43
Total	83
Interest	15
Total Operating Lease Liabilities	68
Delmarva Power and Light Company [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	5
2020	12
2021	12
2022	11
2023	10
Remaining Years	52
Total	102
Interest	19
Total Operating Lease Liabilities	83
Atlantic City Electric Company [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	4
2020	5
2021	5
2022	4
2023	3
Remaining Years	6
Total	27
Interest	2
Total Operating Lease Liabilities	$ 25