Accounts Receivable - Unbilled Customer Revenue (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	$ 629	$ 747
Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	189	240
PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	127	161
Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	139	171
Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	174	175
Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	89	82
Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	50	53
Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	$ 35	$ 40