Lessor - Components of Operating Lease Income (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	$ 54
Variable Lease Income	261
Exelon Generation Co L L C [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	47
Variable Lease Income	258
Commonwealth Edison Co [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	0
Variable Lease Income	0
PECO Energy Co [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	0
Variable Lease Income	0
Baltimore Gas and Electric Company [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	0
Variable Lease Income	0
Pepco Holdings LLC [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	5
Variable Lease Income	3
Potomac Electric Power Company [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	0
Variable Lease Income	0
Delmarva Power & Light Company [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	4
Variable Lease Income	3
Atlantic City Electric Company [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	0
Variable Lease Income	$ 0