v3.25.2
Other Long-Term Assets (Details) - USD ($)
$ in Millions
 9 Months Ended
Jun. 30, 2025
Sep. 30, 2024
Other Long-Term Assets    
Loans and other long-term receivables, net $ 111 $ 84
EnergyRight® receivables, net 56 56
Other Intangible Assets, Net 98 35
Prepaid Expense and Other Assets, Noncurrent 68 62
Prepaid capital assets 67 29
Total other long-term assets 490 344
Prepaid Expense, Current 11 6
Financing Receivable, after Allowance for Credit Loss, Current 3 21
EnergyRight® financing obligation 73 74
Accounts and Financing Receivable, Allowance for Credit Loss 2 2
EnergyRight loan reserve    
Other Long-Term Assets    
Accounts and Financing Receivable, Allowance for Credit Loss 1 1
Economic development loan specific loan reserve    
Other Long-Term Assets    
Accounts and Financing Receivable, Allowance for Credit Loss 1 1
Accounts Receivable [Member]    
Other Long-Term Assets    
EnergyRight® receivables, net 12 12
Other long-term assets    
Other Long-Term Assets    
EnergyRight® receivables, net 44 44
Other 85 88
Other current assets    
Other Long-Term Assets    
Other Intangible Assets, Net 3 13
Other long-term assets    
Other Long-Term Assets    
Commodity Contract Asset, Noncurrent $ 17 $ 2
Energy Right    
Other Long-Term Assets    
Number of days in default 180 days  
Energy Right | Minimum    
Other Long-Term Assets    
Debt Instrument, Term 5 years  
Energy Right | Maximum    
Other Long-Term Assets    
Debt Instrument, Term 10 years