v3.25.2
Fair Value Measurements Fair Value Measurements (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Sep. 30, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Financing Receivable, after Allowance for Credit Loss $ 108   $ 108   $ 99
Investments          
Government debt securities 452   452   457
Corporate debt securities 379   379   378
Mortgage and asset-backed securities 35   35   43
Institutional mutual funds 352   352   342
Forward debt securities contracts 18   18   11
Private credit measured at net asset value 267   267   219
Private equity funds measured at net asset value(1) 868   868   738 [1]
Private real estate funds measured at net asset value(1) 474   474   432 [1]
Commingled funds measured at net asset value(1) 1,446   1,446   1,300 [1]
Total investments 5,277   5,277   4,968
Commodity contract derivatives 6   6   7
Total 5,307   5,307   4,975
Liabilities          
Currency swaps [2] 91   91   116
Interest rate swaps 673   673   840
Commodity contract derivatives 5   5   5
Total 794   794   1,122
Equity Securities, FV-NI 736   736   770
Cash, Cash Equivalents, and Short-Term Investments 250   250   278
Government debt securities reclassed 48   48   95
Commingled funds reclassed 456   456   495
Net Payables 98   98   78
Repurchase Agreements 204   204   174
Commodity Contract under FHP          
Investments          
Total derivatives not subject to master netting or similar arrangement 24   24    
Liabilities          
Derivative Liability, Not Subject to Master Netting Arrangement 25   25   161
NDT [Member]          
Liabilities          
Debt and Equity Securities, Unrealized Gain (Loss) 41 $ 7 12 $ 70  
Debt and Equity Securities, Unrealized Gain (Loss) 41 7 12 70  
ART [Member]          
Liabilities          
Debt and Equity Securities, Unrealized Gain (Loss) 10 1 5 24  
Debt and Equity Securities, Unrealized Gain (Loss) 10 $ 1 5 24  
RP          
Liabilities          
Debt and Equity Securities, Unrealized Gain (Loss)     1 1  
Debt and Equity Securities, Unrealized Gain (Loss)     1 $ 1  
Fair Value, Inputs, Level 1          
Investments          
Government debt securities 408   408   400
Corporate debt securities 0   0   0
Mortgage and asset-backed securities 0   0   0
Institutional mutual funds 352   352   342
Forward debt securities contracts 0   0   0
Private credit measured at net asset value 0   0   0
Private equity funds measured at net asset value(1) 0   0   0 [1]
Private real estate funds measured at net asset value(1) 0   0   0 [1]
Commingled funds measured at net asset value(1) 0   0   0 [1]
Total investments 1,544   1,544   1,607
Commodity contract derivatives 0   0   0
Total 1,544   1,544   1,607
Liabilities          
Currency swaps 0   0   0 [2]
Interest rate swaps 0   0   0
Commodity contract derivatives 0   0   0
Total 0   0   0
Equity Securities, FV-NI 736   736   770
Cash, Cash Equivalents, and Short-Term Investments 48   48   95
Fair Value, Inputs, Level 1 | Commodity Contract under FHP          
Investments          
Total derivatives not subject to master netting or similar arrangement 0   0    
Liabilities          
Derivative Liability, Not Subject to Master Netting Arrangement 0   0   0
Fair Value, Inputs, Level 2          
Investments          
Government debt securities 44   44   57
Corporate debt securities 379   379   378
Mortgage and asset-backed securities 35   35   43
Institutional mutual funds 0   0   0
Forward debt securities contracts 18   18   11
Private credit measured at net asset value 0   0   0
Private equity funds measured at net asset value(1) 0   0   0 [1]
Private real estate funds measured at net asset value(1) 0   0   0 [1]
Commingled funds measured at net asset value(1) 0   0   0 [1]
Total investments 678   678   672
Commodity contract derivatives 6   6   7
Total 708   708   679
Liabilities          
Currency swaps 91   91   116 [2]
Interest rate swaps 673   673   840
Commodity contract derivatives 5   5   5
Total 794   794   1,122
Equity Securities, FV-NI 0   0   0
Cash, Cash Equivalents, and Short-Term Investments 202   202   183
Fair Value, Inputs, Level 2 | Commodity Contract under FHP          
Investments          
Total derivatives not subject to master netting or similar arrangement 24   24    
Liabilities          
Derivative Liability, Not Subject to Master Netting Arrangement 25   25   161
Fair Value, Inputs, Level 3          
Investments          
Government debt securities 0   0   0
Corporate debt securities 0   0   0
Mortgage and asset-backed securities 0   0   0
Institutional mutual funds 0   0   0
Forward debt securities contracts 0   0   0
Private credit measured at net asset value 0   0   0
Private equity funds measured at net asset value(1) 0   0   0 [1]
Private real estate funds measured at net asset value(1) 0   0   0 [1]
Commingled funds measured at net asset value(1) 0   0   0 [1]
Total investments 0   0   0
Commodity contract derivatives 0   0   0
Total 0   0   0
Liabilities          
Currency swaps 0   0   0 [2]
Interest rate swaps 0   0   0
Commodity contract derivatives 0   0   0
Total 0   0   0
Equity Securities, FV-NI 0   0   0
Cash, Cash Equivalents, and Short-Term Investments 0   0   0
Fair Value, Inputs, Level 3 | Commodity Contract under FHP          
Investments          
Total derivatives not subject to master netting or similar arrangement 0   0    
Liabilities          
Derivative Liability, Not Subject to Master Netting Arrangement $ 0   $ 0   $ 0
[1] Certain investments that are measured at fair value using the NAV or its equivalent (alternative investments) have not been categorized in the fair value hierarchy. The inputs to these fair value measurements include underlying NAVs, discounted cash flow valuations, comparable market valuations, and adjustments for currency, credit, liquidity, and other risks. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented on the Consolidated Balance Sheets.
(6) TVA records currency swaps net of cash collateral received from or paid to the counterparty, to the extent such amount is not recorded in Accounts payable and accrued liabilities. See Note 14 — Risk Management Activities and Derivative Transactions — Offsetting of Derivative Assets and Liabilities.
[2] TVA records currency swaps net of cash collateral received from or paid to the counterparty, to the extent such amount is not recorded in Accounts payable and accrued liabilities. See Note 14 — Risk Management Activities and Derivative Transactions — Offsetting of Derivative Assets and Liabilities.