v3.25.2
Debt and Other Obligations Debt Securities Activity (Details) - USD ($)
$ in Millions
9 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Oct. 02, 2024
Sep. 30, 2024
Debt Instrument        
Total long-term debt, net $ 20,880     $ 18,764
Repayments of Unsecured Debt 1,022 [1] $ 22    
Amount of letters of credit outstanding $ 6      
Percent of par value [1] 100.00%      
Long-term power bonds, net $ 19,229     $ 17,867
Repayments of Other Long-term Debt $ 23 $ 17    
Debt Instrument, Redemption, Description 1,045      
Proceeds from Issuance of Debt $ 3,522      
Debt Instrument, Unamortized Discount (Premium), Net 28      
2009 series B        
Debt Instrument        
Repayments of Unsecured Debt 1      
2009 Series B June Payment        
Debt Instrument        
Repayments of Unsecured Debt 21      
2020 Series A Payment        
Debt Instrument        
Repayments of Unsecured Debt $ 1,000      
880591FC1        
Debt Instrument        
Percent of par value 98.517%      
Long-term power bonds, net $ 1,250      
880591FD9        
Debt Instrument        
Percent of par value 99.36%      
Long-term power bonds, net $ 1,500      
Variable Interest Entity, Primary Beneficiary [Member]        
Debt Instrument        
Debt and Lease Obligation     $ 800  
[1]
(3) All redemptions were at 100 percent of par.