Derivative Instruments and Hedging Activities - Schedule of Derivative Assets, Liabilities and the Effects of Offsetting (Details) - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021
Derivative assets:
Fair value of derivative instruments	$ 2,418	$ 1,687
Gross amounts offset in the balance sheet	(295)	(216)
Cash collateral received	(398)	(468)
Total derivative assets – net	1,725	1,003
Derivative liabilities:
Total derivative liabilities – gross	(515)	(317)
Gross amounts offset in the balance sheet	295	216
Cash collateral pledged	7	3
Total derivative liabilities – net	(213)	(98)
Foreign currency contracts
Derivative assets:
Fair value of derivative instruments	119	38
Derivative liabilities:
Total derivative liabilities – gross	(2)	(8)
Commodity contract - subject to PGC and DS mechanisms
Derivative assets:
Fair value of derivative instruments	31	58
Derivative liabilities:
Total derivative liabilities – gross	(26)	(23)
Commodity contracts
Derivative assets:
Fair value of derivative instruments	2,233	1,649
Derivative liabilities:
Total derivative liabilities – gross	(513)	(280)
Interest rate contracts
Derivative assets:
Fair value of derivative instruments	66
Derivative liabilities:
Total derivative liabilities – gross		(29)
Derivatives designated as hedging instruments
Derivative assets:
Fair value of derivative instruments	123	20
Derivatives designated as hedging instruments | Foreign currency contracts
Derivative assets:
Fair value of derivative instruments	57	20
Derivatives designated as hedging instruments | Interest rate contracts
Derivative assets:
Fair value of derivative instruments	66	0
Derivative liabilities:
Total derivative liabilities – gross	0	(29)
Derivatives not designated as hedging instruments
Derivative assets:
Fair value of derivative instruments	2,264	1,609
Derivative liabilities:
Total derivative liabilities – gross	(489)	(265)
Derivatives not designated as hedging instruments | Foreign currency contracts
Derivative assets:
Fair value of derivative instruments	62	18
Derivative liabilities:
Total derivative liabilities – gross	(2)	(8)
Derivatives not designated as hedging instruments | Commodity contracts
Derivative assets:
Fair value of derivative instruments	2,202	1,591
Derivative liabilities:
Total derivative liabilities – gross	$ (487)	$ (257)