Goodwill and Intangible Assets - Schedule of Components of Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Customer relationships	$ 967	$ 985
Trademarks and tradenames	4	4
Noncompete agreements and other	27	27
Accumulated amortization	(712)	(665)
Intangible assets, net (definite-lived)	286	351
Trademarks and tradenames (indefinite-lived)	42	40
Total intangible assets, net	$ 328	$ 391

Finite-Lived Trademarks and Tradenames, Gross

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- Definition

Amount, before amortization, of finite-lived asset representing customer relationship acquired in business combination, asset acquisition, and from joint venture formation.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482665/350-30-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
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-Publisher FASB
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- Definition

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name Accounting Standards Codification
-Section 55
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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- Definition

Gross carrying amount before accumulated amortization as of the balance sheet date of payments made to third parties in exchange for their agreement not to engage in specified competitive practices in specified geographic territories for a specified period of time.

+ References

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Carrying amount (original costs adjusted for previously recognized amortization and impairment) as of the balance sheet date for the rights acquired through registration of a trademark to gain or protect exclusive use of a business name, symbol or other device or style for a projected indefinite period of benefit.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
-SubTopic 30
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-Section 50
-Paragraph 2
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- Definition

Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 350
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-URI https://asc.fasb.org/1943274/2147482665/350-30-50-2

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