Derivative Instruments and Hedging Activities - Fair Value of Derivative Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Derivative assets:
Total derivative assets — gross	$ 189	$ 298	$ 772
Gross amounts offset in the balance sheet	(116)	(124)	(239)
Cash collateral received	(17)	(40)	(108)
Total derivative assets — net	56	134	425
Derivative liabilities:
Total derivative liabilities — gross	(353)	(276)	(453)
Gross amounts offset in the balance sheet	116	124	239
Cash collateral pledged	64	53	45
Total derivative liabilities — net	(173)	(99)	(169)
Commodity contracts
Derivative assets:
Total derivative assets — gross	11	6	18
Derivative liabilities:
Total derivative liabilities — gross	(22)	(8)	(35)
Derivatives designated as hedging instruments:
Derivative assets:
Total derivative assets — gross	20	42	74
Derivative liabilities:
Total derivative liabilities — gross	(17)	0	0
Derivatives designated as hedging instruments: | Foreign currency contracts
Derivative assets:
Total derivative assets — gross	5	14	11
Derivative liabilities:
Total derivative liabilities — gross	(1)	0	0
Derivatives designated as hedging instruments: | Interest rate contracts
Derivative assets:
Total derivative assets — gross	15	28	63
Derivative liabilities:
Total derivative liabilities — gross	(16)	0	0
Derivatives not designated as hedging instruments:
Derivative assets:
Total derivative assets — gross	158	250	680
Derivative liabilities:
Total derivative liabilities — gross	(314)	(268)	(418)
Derivatives not designated as hedging instruments: | Foreign currency contracts
Derivative assets:
Total derivative assets — gross	7	24	24
Derivative liabilities:
Total derivative liabilities — gross	(5)	(2)	(4)
Derivatives not designated as hedging instruments: | Commodity contracts
Derivative assets:
Total derivative assets — gross	151	226	656
Derivative liabilities:
Total derivative liabilities — gross	$ (309)	(266)	$ (414)
Derivatives not designated as hedging instruments: | Commodity contracts | Prepaid expenses and other current assets
Derivative assets:
Total derivative assets — gross		10
Derivatives not designated as hedging instruments: | Commodity contracts | Other current liabilities
Derivative liabilities:
Total derivative liabilities — gross		$ (12)