Stock-Based Employee Benefit Plans - Summary of Assumptions Used to Estimate Fair Value of Stock Options (Details) - Stock Options:	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average expected term (years)	4 years 4 months 24 days	4 years 5 months 15 days	5 years 2 months 23 days
Expected volatility (range), minimum	34.60%	33.60%	33.40%
Expected volatility (range), maximum	36.50%	33.90%	35.50%
Weighted average volatility	35.00%	33.70%	33.50%
Risk free interest rate, minimum	3.89%	4.18%	3.40%
Risk free interest rate, maximum	4.08%	4.30%	4.49%
Weighted average expected dividend yield	0.00%	0.00%	0.00%