Derivative Instruments - Schedule of Fair Value of Derivatives (Details) - Level 2 - USD ($) $ in Millions	Sep. 30, 2026	Sep. 30, 2025
Assets and liabilities measured at fair value on a recurring basis
Net derivative asset / (liability) designated as hedging instruments	$ (58)	$ (32)
Net derivative asset / (liability) not designated as hedging instruments	(1)	(5)
Forward exchange contracts \| Derivatives, Fair Value, by Balance Sheet Location [Axis]: us-gaap:OtherAssetsCurrent
Assets and liabilities measured at fair value on a recurring basis
Forward exchange contracts designated as hedging instruments	10	4
Forward exchange contracts not designated as hedging instruments, other current assets	5	3
Forward exchange contracts \| Derivatives, Fair Value, by Balance Sheet Location [Axis]: us-gaap:OtherAssetsNoncurrent
Assets and liabilities measured at fair value on a recurring basis
Forward exchange contracts designated as hedging instruments	3	1
Forward exchange contracts \| Derivatives, Fair Value, by Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesCurrent
Assets and liabilities measured at fair value on a recurring basis
Forward exchange contracts designated as hedging instruments	(9)	(12)
Forward exchange contracts not designated as hedging instruments, other current liabilities	(6)	(8)
Forward exchange contracts \| Derivatives, Fair Value, by Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent
Assets and liabilities measured at fair value on a recurring basis
Forward exchange contracts designated as hedging instruments	(1)	(3)
Net investment hedges \| Derivatives, Fair Value, by Balance Sheet Location [Axis]: us-gaap:OtherLiabilitiesNoncurrent
Assets and liabilities measured at fair value on a recurring basis
Forward exchange contract designated as hedging instruments	$ (61)	$ (22)

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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Fair value as of the balance sheet date of all foreign currency derivative assets designated as cash flow hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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