Income Taxes - Summary of Income Before Income Tax Provision (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Income before income tax provision:
United States	$ 130,535	$ 254,052	$ 202,643
Other	16,900	7,869	3,151
Income before income tax provision	$ 147,435	$ 261,921	$ 205,794