v3.25.2
Fair Value Measurements - Financial Assets and Liabilities that are Measured at Fair Value on a Recurring Basis (Details) - USD ($)
$ in Millions
Jun. 30, 2025
Sep. 30, 2024
Jun. 30, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: $ 114 $ 140 $ 162
Liabilities: (197) (183) (176)
Commodity contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 3 4 4
Liabilities: (2) (1) (5)
Recurring      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Non-qualified supplemental postretirement grantor trust investments 34 43 42
Recurring | Commodity contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 113 133 137
Liabilities: (158) (152) (174)
Recurring | Foreign currency contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets:   6 18
Liabilities: (25) (9) (2)
Recurring | Interest rate contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 1 1 7
Liabilities: (14) (22)  
Recurring | Level 1      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Non-qualified supplemental postretirement grantor trust investments 34 43 42
Recurring | Level 1 | Commodity contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 100 106 92
Liabilities: (103) (120) (148)
Recurring | Level 1 | Foreign currency contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets:   0 0
Liabilities: 0 0 0
Recurring | Level 1 | Interest rate contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 0 0 0
Liabilities: 0 0  
Recurring | Level 2      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Non-qualified supplemental postretirement grantor trust investments 0 0 0
Recurring | Level 2 | Commodity contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 13 27 45
Liabilities: (55) (32) (26)
Recurring | Level 2 | Foreign currency contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets:   6 18
Liabilities: (25) (9) (2)
Recurring | Level 2 | Interest rate contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 1 1 7
Liabilities: (14) (22)  
Recurring | Level 3      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Non-qualified supplemental postretirement grantor trust investments 0 0 0
Recurring | Level 3 | Commodity contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 0 0 0
Liabilities: 0 0 0
Recurring | Level 3 | Foreign currency contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets:   0 0
Liabilities: 0 0 0
Recurring | Level 3 | Interest rate contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 0 0 $ 0
Liabilities: $ 0 $ 0