Debt and Credit Agreements - Commercial Paper Borrowings (Details) - Commercial Paper [Member] - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Short-term Debt [Line Items]
Commercial Paper	$ 250	$ 599
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.87%	0.35%
Corporate [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 0
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Commercial Paper	0	0
PECO Energy Co [Member]
Short-term Debt [Line Items]
Commercial Paper	0	0
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 250	$ 130
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.87%	0.37%
Pepco Holdings LLC [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 469
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	0.35%
Potomac Electric Power Company [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 175
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	0.33%
Delmarva Power and Light Company [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 149
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	0.36%
Atlantic City Electric Company [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 145
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	0.35%