Income Taxes - Summary of Reconciliation of Changes in Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, beginning balance	$ 2,793	$ 2,887	$ 2,871
Increases in tax positions for prior years		53	15
Decreases in tax positions for prior years	(4)	(35)	(8)
Increases in tax positions for current year	836	519	458
Lapse of the statute of limitations	(182)	(631)	(449)
Unrecognized tax benefits, ending balance	$ 3,443	$ 2,793	$ 2,887