v3.25.1
Fair Value Measurements - Financial Assets and Liabilities that are Measured at Fair Value on a Recurring Basis (Details) - USD ($)
$ in Millions
Mar. 31, 2025
Sep. 30, 2024
Mar. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: $ 256 $ 140 $ 173
Liabilities: (171) (183) (226)
Commodity contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 19 4 8
Liabilities: 0 (1) (14)
Recurring      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Non-qualified supplemental postretirement grantor trust investments 32 43 41
Recurring | Commodity contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 241 133 146
Liabilities: (159) (152) (222)
Recurring | Foreign currency contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 14 6 16
Liabilities: (1) (9) (1)
Recurring | Interest rate contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 1 1 11
Liabilities: (11) (22) (3)
Recurring | Level 1      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Non-qualified supplemental postretirement grantor trust investments 32 43 41
Recurring | Level 1 | Commodity contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 213 106 107
Liabilities: (150) (120) (184)
Recurring | Level 1 | Foreign currency contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 0 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 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: 28 27 39
Liabilities: (9) (32) (38)
Recurring | Level 2 | Foreign currency contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 14 6 16
Liabilities: (1) (9) (1)
Recurring | Level 2 | Interest rate contracts      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis      
Assets: 1 1 11
Liabilities: (11) (22) (3)
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 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 $ 0