v3.26.1
Fair Value Measurements (Quantitative Level 3 Fair Value Disclosures) (Details)
$ in Millions
Mar. 31, 2026
USD ($)
$ / MWh
Dec. 31, 2025
USD ($)
$ / MWh
Mar. 31, 2025
USD ($)
Dec. 31, 2024
USD ($)
Fair Value Measurement Inputs and Valuation Techniques        
Net derivative asset (liability) | $ $ 4 $ 9 $ 3 $ 9
Duke Energy Indiana        
Fair Value Measurement Inputs and Valuation Techniques        
Net derivative asset (liability) | $ 4 9 $ 2 $ 8
Duke Energy Indiana | FTRs | RTO auction pricing        
Fair Value Measurement Inputs and Valuation Techniques        
Net derivative asset (liability) | $ $ 4 $ 9    
Duke Energy Indiana | FTRs | RTO auction pricing | Minimum        
Fair Value Measurement Inputs and Valuation Techniques        
Input measurements (in usd per MWh and usd per MMBtu) | $ / MWh (1.24) (1.00)    
Duke Energy Indiana | FTRs | RTO auction pricing | Maximum        
Fair Value Measurement Inputs and Valuation Techniques        
Input measurements (in usd per MWh and usd per MMBtu) | $ / MWh 15.13 14.63    
Duke Energy Indiana | FTRs | RTO auction pricing | Weighted Average        
Fair Value Measurement Inputs and Valuation Techniques        
Input measurements (in usd per MWh and usd per MMBtu) | $ / MWh 1.11 1.13