Income Taxes - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Income tax computed at statutory rate	$ 33,408	$ 38,356	$ 57,538
State income taxes, net of federal benefit	3,273	2,874	4,482
Permanent differences	9,140	2,037	3,341
Stock-based compensation	1,055	179	(389)
Tax credits	(27,918)	(20,287)	(12,081)
Deferred rate change	53	665	346
Other, net	(101)	134	34
Total expense from income taxes	$ 18,910	$ 23,958	$ 53,271