Goodwill and Other Intangible Assets - Carrying Amount of Goodwill (Details) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2025	Sep. 30, 2024
Goodwill [Roll Forward]
Goodwill, beginning balance		$ 2,164,000,000	$ 2,094,000,000
Business acquisitions			(5,000,000)
Impairments	$ 0	$ (333,000,000)
Goodwill, Impairment Loss, Statement of Income or Comprehensive Income [Extensible Enumeration]		Restructuring and impairment costs
Currency translation and other		$ (24,000,000)	75,000,000
Goodwill, ending balance	1,807,000,000	1,807,000,000	2,164,000,000
Americas
Goodwill [Roll Forward]
Goodwill, beginning balance		606,000,000	609,000,000
Business acquisitions			0
Impairments		0
Currency translation and other		1,000,000	(3,000,000)
Goodwill, ending balance	607,000,000	607,000,000	606,000,000
EMEA
Goodwill [Roll Forward]
Goodwill, beginning balance		341,000,000	317,000,000
Business acquisitions			0
Impairments		(333,000,000)
Currency translation and other		(8,000,000)	24,000,000
Goodwill, ending balance	0	0	341,000,000
Asia
Goodwill [Roll Forward]
Goodwill, beginning balance		1,217,000,000	1,168,000,000
Business acquisitions			(5,000,000)
Impairments		0
Currency translation and other		(17,000,000)	54,000,000
Goodwill, ending balance	$ 1,200,000,000	$ 1,200,000,000	$ 1,217,000,000