Derivative Instruments and Hedging Activities - Fair Value of Derivative Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2024	Sep. 30, 2024	Dec. 31, 2023
Derivative assets:
Total derivative assets — gross	$ 201	$ 140	$ 189
Gross amounts offset in the balance sheet	(83)	(88)	(116)
Cash collateral received	(31)	(14)	(17)
Total derivative assets — net	87	38	56
Derivative liabilities:
Total derivative liabilities — gross	(122)	(183)	(353)
Gross amounts offset in the balance sheet	83	88	116
Cash collateral pledged	4	36	64
Total derivative liabilities — net	(35)	(59)	(173)
Commodity contracts
Derivative assets:
Total derivative assets — gross	6	4	11
Derivative liabilities:
Total derivative liabilities — gross	0	(1)	(22)
Derivatives designated as hedging instruments:
Derivative assets:
Total derivative assets — gross	24	7	20
Derivative liabilities:
Total derivative liabilities — gross	(9)	(22)	(17)
Derivatives designated as hedging instruments: | Foreign currency contracts
Derivative assets:
Total derivative assets — gross	19	6	5
Derivative liabilities:
Total derivative liabilities — gross	0	0	(1)
Derivatives designated as hedging instruments: | Interest rate contracts
Derivative assets:
Total derivative assets — gross	5	1	15
Derivative liabilities:
Total derivative liabilities — gross	(9)	(22)	(16)
Derivatives not designated as hedging instruments:
Derivative assets:
Total derivative assets — gross	171	129	158
Derivative liabilities:
Total derivative liabilities — gross	(113)	(160)	(314)
Derivatives not designated as hedging instruments: | Foreign currency contracts
Derivative assets:
Total derivative assets — gross	14	0	7
Derivative liabilities:
Total derivative liabilities — gross	(1)	(9)	(5)
Derivatives not designated as hedging instruments: | Commodity contracts
Derivative assets:
Total derivative assets — gross	157	129	151
Derivative liabilities:
Total derivative liabilities — gross	$ (112)	$ (151)	$ (309)