Share-based Compensation - Summary of Option Activity (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Sep. 30, 2024	Sep. 30, 2023
Stock Options Additional Disclosures
Stock price used to calculate aggregate intrinsic value (in dollars per share)	$ 274.95	$ 230.01
Stock Option
Options
Beginning balance (in shares)	5,925,355
Granted (in shares)	722,695
Forfeited (in shares)	(39,776)
Exercised (in shares)	(1,243,542)
Ending balance (in shares)	5,364,732
Options exercisable at end of period (in shares)	3,862,434
Options exercisable and expected to vest at end of period (in shares)	5,323,802
Weighted- Average Exercise Price
Beginning balance (in dollars per share)	$ 162.40
Granted (in dollars per share)	249.56
Forfeited (in dollars per share)	220.53
Exercised (in dollars per share)	122.21
Ending balance (in dollars per share)	183.02
Options exercisable at end of period (in dollars per share)	165.79
Options exercisable and expected to vest at end of period (in dollars per share)	$ 182.59
Stock Options Additional Disclosures
Weighted-average remaining contractual term, Outstanding as of September 30, 2024	5 years 11 months 15 days
Weighted-average remaining contractual term, Options exercisable as of September 30, 2024	5 years 3 days
Weighted-average remaining contractual term, Options exercisable and expected to vest as of September 30, 2024	5 years 11 months 8 days
Aggregate intrinsic value, Outstanding as of September 30, 2024	$ 493
Aggregate intrinsic value, Options exercisable as of September 30, 2024	422
Aggregate intrinsic value, Options exercisable and expected to vest at September 30, 2024	$ 492

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Number of options outstanding, including both vested and non-vested options.

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