v3.25.2
Risk Management Activities and Derivative Transactions Derivative Instruments That Do Not Receive Hedge Accounting Treatment (Details)
 3 Months Ended 9 Months Ended
Jun. 30, 2025
USD ($)
Jun. 30, 2024
USD ($)
Jun. 30, 2025
USD ($)
Jun. 30, 2024
USD ($)
Sep. 30, 2024
USD ($)
Derivative          
Change in Unrealized gains (losses) on Interest Rate Derivatives $ (6,000,000) $ 32,000,000 $ (141,000,000) $ 63,000,000  
Fair value 8,000,000   8,000,000   $ 64,000,000
Interest Rate Swap          
Derivative          
Amount recognized for unrealized gains (losses)     0    
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net $ (11,000,000) (8,000,000) [1] $ (33,000,000) [1] (23,000,000) [1]  
Commodity Contract Derivatives          
Derivative          
Number of contracts 57   57   45
Derivative, Nonmonetary Notional Amount 412,000,000   412,000,000   321,000,000
Fair value $ 1,000,000   $ 1,000,000   $ 2,000,000
Derivative, Term of Contract 10 years        
Derivative, Term of Contract 10 years        
Commodity Contract under FHP          
Derivative          
Number of contracts 210   210   126
Derivative, Nonmonetary Notional Amount 284   284   230
Fair value $ (1,000,000)   $ (1,000,000)   $ (161,000,000)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net $ (13,000,000) $ (72,000,000) $ (64,000,000) $ (227,000,000)  
Derivative, Term of Contract 5 years        
Derivative, Term of Contract 5 years        
[1] All of TVA's derivative instruments that do not receive hedge accounting treatment have unrealized gains (losses) that would otherwise be recognized in income but instead are deferred as regulatory assets and liabilities. As such, there were no related gains (losses) recognized in income for these unrealized gains (losses) for the three and nine months ended June 30, 2025 and for the three and nine months ended June 30, 2024.
(2) Of the amount recognized for the three months ended June 30, 2025, $3 million and $10 million were reported in Fuel expense and Purchased power expense, respectively, and of the amount recognized for the three months ended June 30, 2024, $59 million and $13 million were reported in Fuel expense and Purchased power expense, respectively. Of the amount recognized for the nine months ended June 30, 2025, $12 million and $52 million were reported in Fuel expense and Purchased power expense, respectively, and of the amount recognized for the nine months ended June 30, 2024, $186 million and $41 million were reported in Fuel expense and Purchased power expense, respectively.