Share-based Compensation - Summary of RSU Activity (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Aggregate Intrinsic Value
Stock price used to calculate aggregate intrinsic value (in dollars per share)	$ 274.95	$ 230.01
Restricted Stock Units (RSUs)
Units
Beginning balance (in shares)	6,417,397
Granted (in shares)	3,221,842
Vested (in shares)	(2,953,860)
Forfeited (in shares)	(325,718)
Ending balance (in shares)	6,359,661	6,417,397
Weighted- Average Grant Date Fair Value
Beginning balance (in dollars per share)	$ 209.19
Granted (in dollars per share)	253.29	$ 212.94	$ 204.73
Vested (in dollars per share)	208.69
Forfeited (in dollars per share)	224.82
Ending balance (in dollars per share)	$ 230.99	$ 209.19
Weighted- Average Remaining Contractual Term (in years)
Outstanding as of September 30, 2024	11 months 4 days
Aggregate Intrinsic Value
Outstanding as of September 30, 2024	$ 1,749

No definition available.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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

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-Topic 718
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-Section 50
-Paragraph 2
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 718
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-Name Accounting Standards Codification
-Paragraph 2
-Section 50
-Publisher FASB
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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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Price of a single share of a number of saleable stocks of a company.

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Intrinsic value of outstanding award under share-based payment arrangement. Excludes share and unit options.

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