Derivative Instruments and Hedging Activities - Fair Value of Derivative Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2024	Sep. 30, 2023
Derivative assets:
Total derivative assets – gross	$ 140	$ 298
Gross amounts offset in the balance sheet	(88)	(124)
Cash collateral received	(14)	(40)
Total derivative assets – net	38	134
Derivative liabilities:
Total derivative liabilities – gross	(183)	(276)
Gross amounts offset in the balance sheet	88	124
Cash collateral pledged	36	53
Total derivative liabilities – net	(59)	(99)
Interest rate contracts
Derivative liabilities:
Total derivative liabilities – gross	(22)
Commodity contracts
Derivative assets:
Total derivative assets – gross	4	6
Derivative liabilities:
Total derivative liabilities – gross	(1)	(8)
Derivatives designated as hedging instruments:
Derivative assets:
Total derivative assets – gross	7	42
Derivatives designated as hedging instruments: | Foreign currency contracts
Derivative assets:
Total derivative assets – gross	6	14
Derivatives designated as hedging instruments: | Interest rate contracts
Derivative assets:
Total derivative assets – gross	1	28
Derivative liabilities:
Total derivative liabilities – gross	(22)	0
Derivatives not designated as hedging instruments:
Derivative assets:
Total derivative assets – gross	129	250
Derivative liabilities:
Total derivative liabilities – gross	(160)	(268)
Derivatives not designated as hedging instruments: | Foreign currency contracts
Derivative assets:
Total derivative assets – gross	0	24
Derivative liabilities:
Total derivative liabilities – gross	(9)	(2)
Derivatives not designated as hedging instruments: | Commodity contracts
Derivative assets:
Total derivative assets – gross	129	226
Derivative liabilities:
Total derivative liabilities – gross	$ (151)	$ (266)