Retirement Plans - Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Change in Projected Benefit Obligation:
Service cost	$ 6	$ 6	$ 5
Interest cost	16	19	18
Pension plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Accumulated Benefit Obligation	346	366
Change in Projected Benefit Obligation:
Projected benefit obligation at beginning of year	384	349
Service cost	6	5
Interest cost	16	19
Actuarial loss (gain)	(14)	28
Benefits paid	(21)	(28)
Curtailments, settlements and other	(12)	(6)
Currency translation adjustment	7	17
Projected benefit obligation at end of year	366	384	349
Change in Plan Assets:
Fair value of plan assets at beginning of year	293	263
Actual return on plan assets	(6)	26
Employer contributions, net	18	20
Benefits paid	(21)	(28)
Curtailments, settlements and other	(12)	(6)
Currency translation adjustment	1	18
Fair value of plan assets at end of year	273	293	$ 263
Funded status	(93)	(91)
Pension plan assets (other noncurrent assets) | Pension plan
Change in Plan Assets:
Funded status	25	19
Pension benefits (of which $6 million and $5 million are included in accrued compensation and benefits, respectively) | Pension plan
Change in Plan Assets:
Funded status	(118)	(110)
Pension and postretirement benefits | Pension plan
Change in Plan Assets:
Funded status	$ 6	$ 5