v3.26.3
Fair Value of Financial Assets and Liabilities - Fair Value Inputs Assets Quantitative Information (Details) - Fair Value, Inputs, Level 3 [Member] - Derivative [Member] - USD ($)
Sep. 30, 2026
Dec. 31, 2025
Derivatives, Fair Value [Line Items]    
Derivative Liability, Fair Value, Amount Not Offset Against Collateral $ (117,000,000) $ (131,000,000)
Discounted Cash Flow [Member] | Minimum [Member]    
Derivatives, Fair Value [Line Items]    
Fair Value Inputs Forward Power Price 26.75 29.75
Discounted Cash Flow [Member] | Maximum [Member]    
Derivatives, Fair Value [Line Items]    
Fair Value Inputs Forward Power Price 66.55 61.84
Discounted Cash Flow [Member] | Arithmetic Average [Member]    
Derivatives, Fair Value [Line Items]    
Fair Value Inputs Forward Power Price 43.02 41.95
Commonwealth Edison Co    
Derivatives, Fair Value [Line Items]    
Derivative Liability, Fair Value, Amount Not Offset Against Collateral $ (117,000,000) $ (131,000,000)
Commonwealth Edison Co | Discounted Cash Flow [Member] | Minimum [Member]    
Derivatives, Fair Value [Line Items]    
Fair Value Inputs Forward Power Price 26.75 29.75
Commonwealth Edison Co | Discounted Cash Flow [Member] | Maximum [Member]    
Derivatives, Fair Value [Line Items]    
Fair Value Inputs Forward Power Price 66.55 61.84
Commonwealth Edison Co | Discounted Cash Flow [Member] | Arithmetic Average [Member]    
Derivatives, Fair Value [Line Items]    
Fair Value Inputs Forward Power Price 43.02 41.95