Income Taxes - Allocation of Tax Benefits (Details) - USD ($) $ in Millions	Sep. 30, 2026	Sep. 30, 2025
Atlantic City Electric Company
Income Tax Contingency [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	$ 3	$ 4
Pepco Holdings LLC
Income Tax Contingency [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	21	23
Commonwealth Edison Co
Income Tax Contingency [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	125	20
PECO Energy Co
Income Tax Contingency [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	27	14
Baltimore Gas and Electric Company
Income Tax Contingency [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	(3)	12
Potomac Electric Power Company
Income Tax Contingency [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	8	12
Delmarva Power and Light Company
Income Tax Contingency [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	$ 9	$ 7