Stock-Based Compensation - Schedule of Assumptions for Stock Options Granted (Details) - Performance-based restricted stock - $ / 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 volatility, minimum (percentage)	36.30%	32.50%	41.50%
Expected volatility, maximum (percentage)	82.70%	84.60%	86.90%
Risk-free interest rate	4.22%	4.57%	4.26%
Dividend yield	0.00%	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant-date stock price (in dollars per share)	$ 10.49	$ 9.81	$ 10.31
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant-date stock price (in dollars per share)	$ 179.41	$ 142.79	$ 93.50