Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Deferred tax assets:
Loss and credit carryforwards	$ 6,876	$ 7,717
Compensation benefits	31,638	32,093
Operating lease liabilities	7,375	7,881
Research and development costs	100,304	67,795
Other assets	21,538	18,241
Total deferred tax assets	167,731	133,727
Deferred tax liabilities:
Intangible assets	(8,612)	(7,812)
Deferred commission	(15,134)	(14,484)
Operating lease right-of-use assets	(6,479)	(7,240)
Other liabilities	(18,953)	(17,678)
Total deferred tax liabilities	(49,178)	(47,214)
Deferred tax assets, net	$ 118,553	$ 86,513