v3.26.1
Fair Value of Financial Assets and Liabilities - Fair Value Inputs Assets Quantitative Information (Details) - Fair Value, Inputs, Level 3 [Member] - Derivative [Member] - USD ($)
Jun. 30, 2026
Dec. 31, 2025
Derivatives, Fair Value [Line Items]    
Derivative Liability, Fair Value, Amount Not Offset Against Collateral $ (128,000,000) $ (131,000,000)
Discounted Cash Flow [Member] | Minimum [Member]    
Derivatives, Fair Value [Line Items]    
Fair Value Inputs Forward Power Price 24.82 29.75
Discounted Cash Flow [Member] | Maximum [Member]    
Derivatives, Fair Value [Line Items]    
Fair Value Inputs Forward Power Price 68.10 61.84
Discounted Cash Flow [Member] | Arithmetic Average [Member]    
Derivatives, Fair Value [Line Items]    
Fair Value Inputs Forward Power Price 40.37 41.95
Commonwealth Edison Co    
Derivatives, Fair Value [Line Items]    
Derivative Liability, Fair Value, Amount Not Offset Against Collateral $ (128,000,000) $ (131,000,000)
Commonwealth Edison Co | Discounted Cash Flow [Member] | Minimum [Member]    
Derivatives, Fair Value [Line Items]    
Fair Value Inputs Forward Power Price 24.82 29.75
Commonwealth Edison Co | Discounted Cash Flow [Member] | Maximum [Member]    
Derivatives, Fair Value [Line Items]    
Fair Value Inputs Forward Power Price 68.10 61.84
Commonwealth Edison Co | Discounted Cash Flow [Member] | Arithmetic Average [Member]    
Derivatives, Fair Value [Line Items]    
Fair Value Inputs Forward Power Price 40.37 41.95