Derivative Instruments and Hedging Activities - Fair Value of Derivative Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2022	Sep. 30, 2021	Jun. 30, 2021
Derivative assets:
Total derivative assets — gross	$ 2,068	$ 1,687	$ 661
Gross amounts offset in the balance sheet	(226)	(216)	(77)
Cash collateral received	(659)	(468)	(105)
Total derivative assets — net	1,183	1,003	479
Derivative liabilities:
Total derivative liabilities — gross	(363)	(317)	(193)
Gross amounts offset in the balance sheet	226	216	77
Cash collateral pledged	13	3	0
Total derivative liabilities — net	(124)	(98)	(116)
Commodity contracts
Derivative assets:
Total derivative assets — gross	30	58	14
Derivative liabilities:
Total derivative liabilities — gross	(23)	(23)	(6)
Derivatives designated as hedging instruments:
Derivative assets:
Total derivative assets — gross	72	20	15
Derivatives designated as hedging instruments: | Foreign currency contracts
Derivative assets:
Total derivative assets — gross	28	20	15
Derivatives designated as hedging instruments: | Interest rate contracts
Derivative assets:
Total derivative assets — gross	44	0	0
Derivative liabilities:
Total derivative liabilities — gross	0	(29)	(35)
Derivatives not designated as hedging instruments:
Derivative assets:
Total derivative assets — gross	1,966	1,609	632
Derivative liabilities:
Total derivative liabilities — gross	(340)	(265)	(152)
Derivatives not designated as hedging instruments: | Foreign currency contracts
Derivative assets:
Total derivative assets — gross	31	18	9
Derivative liabilities:
Total derivative liabilities — gross	(2)	(8)	(13)
Derivatives not designated as hedging instruments: | Commodity contracts
Derivative assets:
Total derivative assets — gross	1,935	1,591	623
Derivative liabilities:
Total derivative liabilities — gross	$ (338)	$ (257)	$ (139)