Retirement Plans - Components and Assumptions of Net Periodic Benefit Cost (Credit) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 6	$ 5	$ 7
Interest cost	19	18	10
Expected return on plan assets	$ (12)	$ (12)	$ (14)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other pension expense (income)	Other pension expense (income)	Other pension expense (income)
Net actuarial loss (gain)	$ 13	$ 19	$ (7)
Settlement loss	1	8	1
Net periodic benefit cost (credit)	27	38	$ (3)
Pension plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	5	5
Interest cost	$ 19	$ 18
Pension plan | U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	5.87%	5.51%	3.06%
Expected return on plan assets	6.75%	6.75%	6.75%
Pension plan | Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Discount rate	5.60%	4.98%	2.14%
Expected return on plan assets	4.95%	4.53%	3.20%
Rate of compensation increase	4.53%	4.43%	4.05%