Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, Assets	$ 2,418	$ 1,687
Derivative instrument, Liabilities	515	317
Non-qualified supplemental postretirement grantor trust investments	43	53
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-qualified supplemental postretirement grantor trust investments	43	53
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-qualified supplemental postretirement grantor trust investments	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Non-qualified supplemental postretirement grantor trust investments	0	0
Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, Assets	2,233	1,649
Derivative instrument, Liabilities	513	280
Commodity contracts | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, Assets	938	641
Derivative instrument, Liabilities	377	264
Commodity contracts | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, Assets	1,268	1,008
Derivative instrument, Liabilities	136	16
Commodity contracts | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, Assets	27	0
Derivative instrument, Liabilities	0	0
Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, Assets	119	38
Derivative instrument, Liabilities	2	8
Foreign currency contracts | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, Assets	0	0
Derivative instrument, Liabilities	0	0
Foreign currency contracts | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, Assets	119	38
Derivative instrument, Liabilities	2	8
Foreign currency contracts | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, Assets	0	0
Derivative instrument, Liabilities	0	0
Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, Assets	66
Derivative instrument, Liabilities		29
Interest rate contracts | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, Assets	0
Derivative instrument, Liabilities		0
Interest rate contracts | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, Assets	66
Derivative instrument, Liabilities		29
Interest rate contracts | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, Assets	$ 0
Derivative instrument, Liabilities		$ 0