Stock-Based Employee Benefit Plans - Summary of ESPP activities (Details) - $ / shares	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
ESPP, Discount from Market Price, Purchase Date	15.00%
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
ESPP, Discount from Market Price, Purchase Date	85.00%
ESPP, shares issued in period	12,455	13,721	21,876
ESPP, per share weighted average price of shares purchased	$ 1,457.57	$ 1,217.05	$ 646.37