Employee Benefit Plans - Change in Projected Benefit Obligations and Change in Plan Assets (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Change in Plan Assets:
Fair value of plan assets at beginning of year	$ 156
Fair value of plan assets at end of year	151	$ 156
Pension Benefits [Member] | U.S. Defined Benefit Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	2	2
Benefit obligation at end of year	2	2	$ 2
Change in Plan Assets:
Funded status	(2)	(2)
Recognized asset (liability)	(2)	(2)
Pension Benefits [Member] | Foreign Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	155	139
Service cost	3	3	3
Interest cost	$ 6	$ 8	7
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)
Plan participants’ contribution	$ 1	$ 1
Foreign currency exchange rate changes		5
(Gain) loss from changes in actuarial assumptions and plan experience	(4)	12
Benefits paid	(8)	(8)
Plan Amendments	3
Settlements or curtailments	$ (4)	$ (5)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Settlement and Curtailment Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)	Other income (expense)
Benefit obligation at end of year	$ 152	$ 155	139
Change in Plan Assets:
Fair value of plan assets at beginning of year	156	144
Actual return on plan assets	3	13
Employer contribution	4	4
Plan participants’ contribution	1	1
Foreign currency exchange rate changes	(1)	7
Benefits paid	(8)	(8)
Settlements or curtailments	(4)	(5)
Fair value of plan assets at end of year	151	156	144
Funded status	(1)	1
Recognized asset (liability)	(1)	1
Postretirement Benefits [Member] | U.S. Defined Benefit Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	13	14
Interest cost	$ 1	1	1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income (expense)
(Gain) loss from changes in actuarial assumptions and plan experience		1
Benefits paid	$ (2)	(2)
Benefit obligation at end of year	12	13	14
Change in Plan Assets:
Employer contribution	2	2
Benefits paid	(2)	(2)
Funded status	(12)	(13)
Recognized asset (liability)	(12)	(13)
Postretirement Benefits [Member] | Foreign Plans [Member]
Change in Benefit Obligations:
Benefit obligation at beginning of year	12	11
Interest cost		$ 1	1
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]		Other income (expense)
(Gain) loss from changes in actuarial assumptions and plan experience		$ 2
Benefits paid	(1)	(1)
Settlements or curtailments		$ (1)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Settlement and Curtailment Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		Other income (expense)
Benefit obligation at end of year	11	$ 12	$ 11
Change in Plan Assets:
Employer contribution	1	2
Benefits paid	(1)	(1)
Settlements or curtailments		(1)
Funded status	(11)	(12)
Recognized asset (liability)	$ (11)	$ (12)