Fair Value Measurements - Financial Assets and Liabilities that are Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative instruments, Assets	$ 1,156	$ 1,687	$ 185
Derivative instruments, Liabilities	(202)	(317)	(147)
Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative instruments, Assets	10	58	1
Derivative instruments, Liabilities	(7)	(23)	(2)
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Non-qualified supplemental postretirement grantor trust investments	52	53	46
Recurring | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative instruments, Assets	1,122	1,649	171
Derivative instruments, Liabilities	(178)	(280)	(72)
Recurring | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative instruments, Assets	29	38	14
Derivative instruments, Liabilities	(7)	(8)	(25)
Recurring | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative instruments, Assets	5
Derivative instruments, Liabilities	(17)	(29)	(50)
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Non-qualified supplemental postretirement grantor trust investments	52	53	46
Recurring | Level 1 | Commodity contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative instruments, Assets	411	641	60
Derivative instruments, Liabilities	(160)	(264)	(58)
Recurring | Level 1 | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative instruments, Assets	0	0	0
Derivative instruments, Liabilities	0	0	0
Recurring | Level 1 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative instruments, Assets	0
Derivative instruments, 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
Derivative instruments, Assets	711	1,008	111
Derivative instruments, Liabilities	(18)	(16)	(14)
Recurring | Level 2 | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative instruments, Assets	29	38	14
Derivative instruments, Liabilities	(7)	(8)	(25)
Recurring | Level 2 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative instruments, Assets	5
Derivative instruments, Liabilities	(17)	(29)	(50)
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
Derivative instruments, Assets	0	0	0
Derivative instruments, Liabilities	0	0	0
Recurring | Level 3 | Foreign currency contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative instruments, Assets	0	0	0
Derivative instruments, Liabilities	0	0	0
Recurring | Level 3 | Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Derivative instruments, Assets	0
Derivative instruments, Liabilities	$ 0	$ 0	$ 0