Employee Benefit Plans - Net Periodic Defined Benefit Pension and Other Postretirement Benefit Costs (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)	Other income (expense)
Settlements or Curtailments cost			$ 4
Net periodic (benefit) cost			4
Pension Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 4	6
Interest cost	7	4	3
Expected return on plan assets	$ (7)	$ (6)	$ (10)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)	Other income (expense)
Amortization of net losses	$ (1)	$ 1	$ 3
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)	Other income (expense)
Settlements or Curtailments cost			$ 1
Other			2
Net periodic (benefit) cost	$ 2	$ 3	5
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1
Amortization of net losses	$ (1)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)
Settlements or Curtailments cost		$ (1)
Net periodic (benefit) cost		(1)
Postretirement Benefits [Member] | Foreign Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 1	$ 1	$ 1
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)	Other income (expense)
Net periodic (benefit) cost	$ 1	$ 1	$ 1