Stock-based Compensation - Share-Based Payment Arrangement, Option, Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Share-Based Payment Arrangement [Abstract]
Weighted-average grant-date fair value of options granted (in dollars per share)	$ 18.21	$ 18.59	$ 9.36
Intrinsic value of options exercised (in millions)	$ 27	$ 19	$ 94

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration