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Fair Value Measurements (Quantitative Level 3 Fair Value Disclosure) (Details)
$ in Millions
Dec. 31, 2025
USD ($)
$ / MWh
Dec. 31, 2024
USD ($)
$ / MWh
Dec. 31, 2023
USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Fair value | $ $ 9 $ 9 $ 15
Duke Energy Ohio | FTR price – per MWh | RTO auction pricing      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Fair value | $   $ 1  
Duke Energy Ohio | FTR price – per MWh | Maximum | RTO auction pricing      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Input measurement (in usd per MWh and usd per MMBtu)   1.13  
Duke Energy Ohio | FTR price – per MWh | Weighted Average | RTO auction pricing      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Input measurement (in usd per MWh and usd per MMBtu)   0.48  
Duke Energy Indiana      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Fair value | $ 9 $ 8 $ 13
Duke Energy Indiana | FTR price – per MWh | RTO auction pricing      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Fair value | $ $ 9 $ 8  
Duke Energy Indiana | FTR price – per MWh | Minimum | RTO auction pricing      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Input measurement (in usd per MWh and usd per MMBtu) (1.00) (0.63)  
Duke Energy Indiana | FTR price – per MWh | Maximum | RTO auction pricing      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Input measurement (in usd per MWh and usd per MMBtu) 14.63 9.24  
Duke Energy Indiana | FTR price – per MWh | Weighted Average | RTO auction pricing      
Fair Value Measurement Inputs and Valuation Techniques [Line Items]      
Input measurement (in usd per MWh and usd per MMBtu) 1.13 0.94