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Fair Value Measurements (Reconciliation of Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Unobservable Inputs) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Derivatives (net)    
Balance at beginning of period $ 9 $ 15
Purchases, sales, issuances and settlements:    
Purchases 14 29
Settlements (6) (46)
Net transfers Out of Level 3 (7)  
Total (losses) gains included on the Consolidated Balance Sheet (1) 11
Ending balance 9 9
Duke Energy Indiana    
Derivatives (net)    
Balance at beginning of period 8 13
Purchases, sales, issuances and settlements:    
Purchases 12 27
Settlements (4) (42)
Total (losses) gains included on the Consolidated Balance Sheet   10
Ending balance $ 9 $ 8