Share-based Compensation - Summary of Performance-based Shares Activity (Detail) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2022 USD ($) $ / shares shares
Aggregate Intrinsic Value
Stock price used to calculate aggregate intrinsic value (in dollars per share)	$ 177.65
Performance-based Shares
Shares
Beginning balance (in shares) | shares	863,860
Granted (in shares) | shares	440,722
Vested and earned (in shares) | shares	(245,922)
Unearned (in shares) | shares	(200,800)
Forfeited (in shares) | shares	(23,664)
Ending balance (in shares) | shares	834,196
Weighted- Average Grant Date Fair Value
Beginning balance (in dollars per share)	$ 204.82
Granted (in dollars per share)	186.50
Vested and earned (in dollars per share)	200.90
Unearned (in dollars per share)	190.43
Forfeited (in dollars per share)	199.20
Ending balance (in dollars per share)	$ 199.92
Weighted- Average Remaining Contractual Term (in years)
Outstanding at September 30, 2022	10 months 20 days
Aggregate Intrinsic Value
Outstanding at September 30, 2022 | $	$ 148