Share-based Compensation - Assumptions Used to Estimate Fair Value Using Monte Carlo Model (Details) - Performance-based Shares - $ / shares	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	2 years 18 days	2 years	1 year 10 months 24 days
Risk-free rate of return	0.50%	0.20%	1.60%
Expected volatility	28.30%	27.20%	20.90%
Expected dividend yield	0.80%	0.60%	0.70%
Fair value per performance-based share granted (in dollars per share)	$ 186.50	$ 229.81	$ 211.08