Benefit Plans - Net Pension and Other Postretirement Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plan Disclosure [Line Items]
Net pension cost	$ 65	$ 98	$ 17
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	88	91	134
Interest cost	139	129	77
Expected return on plan assets	(150)	(141)	(187)
Amortization of prior service credit	(4)	(7)	(15)
Amortization of loss	57	58	61
Curtailments/settlement loss	1	44	73
Net pension cost	131	174	143
International plans | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Net pension cost	$ 28	$ 25	$ 20