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Fair Value of Financial Assets and Liabilities - Fair Value Reconciliation of Level 3 Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Purchases, sales, issuances and settlements    
Market-to-market derivative liabilities, current $ 74 $ 8
Derivative Liability, Noncurrent 106 83
Fair Value, Inputs, Level 3 [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Beginning Balance (44) (182)
Total realized / unrealized gains (losses)    
Included in net income 3 5
Included in regulatory assets/liabilities (49) 135
Purchases, sales, issuances and settlements    
Transfers into Level 3   (2)
Ending Balance (90) (44)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss) 3 5
Commonwealth Edison Co    
Purchases, sales, issuances and settlements    
Market-to-market derivative liabilities, current 27 5
Derivative Liability, Noncurrent 106 79
Commonwealth Edison Co | Fair Value, Inputs, Level 3 [Member]    
Purchases, sales, issuances and settlements    
Market-to-market derivative liabilities, current 27 5
Derivative Liability, Noncurrent 106 79
Commonwealth Edison Co | Derivative [Member] | Interest Rate Swap    
Purchases, sales, issuances and settlements    
Realized Investment Gains (Losses) 34 (1)
Commonwealth Edison Co | Derivative [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Beginning Balance (84) (219)
Total realized / unrealized gains (losses)    
Included in net income 0 0
Included in regulatory assets/liabilities (49) 135
Purchases, sales, issuances and settlements    
Transfers into Level 3   0
Ending Balance (133) (84)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss) 0 0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Period Increase (Decrease) (83) (136)
Pepco Holdings LLC | 6311 Life Insurance [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Beginning Balance 40 35
Total realized / unrealized gains (losses)    
Included in net income 1 5
Included in regulatory assets/liabilities 0 0
Purchases, sales, issuances and settlements    
Transfers into Level 3   0
Ending Balance 41 40
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss) 1 5
Potomac Electric Power Company | 6311 Life Insurance [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]    
Beginning Balance 40 35
Total realized / unrealized gains (losses)    
Included in net income 1 5
Included in regulatory assets/liabilities 0 0
Purchases, sales, issuances and settlements    
Transfers into Level 3   0
Ending Balance 41 40
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss) $ 1 $ 5