Share-Based Compensation - Assumptions for Estimation of Fair Values of Stock Appreciation Rights Granted During Reporting Periods (Details) - Stock Appreciation Rights (SARs) - $ / shares	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	4.51%	3.78%	1.41%
Expected volatility	22.00%	21.00%	22.00%
Expected dividend yield	1.59%	1.53%	1.42%
Expected life	7 years	7 years	7 years 3 months 18 days
Fair value derived (in USD per share)	$ 63.05	$ 57.80	$ 49.45