Income Taxes - Reconciliation of the Federal Statutory Tax Rate to the Total Tax Provision (Benefit) (Detail)	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Income Tax Disclosure [Abstract]
Federal income taxes computed at the statutory rate	21.00%	21.00%
State income taxes, net of federal benefit	1.20%	1.20%
Unrecognized tax benefits	3.00%	5.80%
Research and development tax credit	(1.80%)
Foreign-derived intangible income deduction	(1.00%)	(0.30%)
Other, net	0.10%	2.10%
Effective income tax rate	22.50%	29.80%