Derivative Instruments and Hedging Activities - Schedule of Derivative Assets, Liabilities and the Effects of Offsetting (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Derivative assets:
Total derivative assets – gross	$ 97	$ 140
Gross amounts offset in the balance sheet	(65)	(88)
Cash collateral received	(2)	(14)
Total derivative assets – net	30	38
Derivative liabilities:
Total derivative liabilities – gross	(164)	(183)
Gross amounts offset in the balance sheet	65	88
Cash collateral pledged	19	36
Total derivative liabilities – net	(80)	(59)
Interest rate contracts
Derivative liabilities:
Total derivative liabilities – gross		(22)
Commodity contracts
Derivative assets:
Total derivative assets – gross	3	4
Derivative liabilities:
Total derivative liabilities – gross	(8)	(1)
Derivatives designated as hedging instruments:
Derivative assets:
Total derivative assets – gross	1	7
Derivatives designated as hedging instruments: | Foreign currency contracts
Derivative assets:
Total derivative assets – gross	1	6
Derivatives designated as hedging instruments: | Interest rate contracts
Derivative assets:
Total derivative assets – gross	0	1
Derivative liabilities:
Total derivative liabilities – gross	(12)	(22)
Derivatives not designated as hedging instruments:
Derivative liabilities:
Total derivative liabilities – gross	(144)	(160)
Derivatives not designated as hedging instruments: | Foreign currency contracts
Derivative liabilities:
Total derivative liabilities – gross	(19)	(9)
Derivatives not designated as hedging instruments: | Commodity contracts
Derivative assets:
Total derivative assets – gross	93	129
Derivative liabilities:
Total derivative liabilities – gross	$ (125)	$ (151)