Share-based Compensation - Schedule of Assumptions Used to Estimate Fair Value Using Monte Carlo Model (Details) - Performance-based Shares - $ / shares	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	1 year 8 months 12 days	1 year 11 months 4 days	2 years 1 month 24 days
Risk-free rate of return (in percent)	4.20%	4.80%	4.40%
Expected volatility (in percent)	19.00%	21.70%	28.90%
Expected dividend yield (in percent)	0.80%	0.80%	0.80%
Fair value per performance-based share granted (in dollars per share)	$ 345.65	$ 281.85	$ 221.32