Long-Term Debt and Bank Facility Borrowings - Company's Debt (Detail) - USD ($) $ in Thousands		Jun. 30, 2025	Sep. 30, 2024
Debt Instrument [Line Items]
Long-term debt, carrying Amount		$ 193,297	$ 208,816
Current maturities of long-term debt, carrying Amount		21,000	21,005
Long-term debt	[1]	172,297	187,811
Long-term debt, fair value	[2]	194,250	210,005
Current maturities of long-term debt, fair value	[2]	21,000	21,005
Long-term portion of debt, fair value	[1],[2]	173,250	189,000
Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility borrowings, carrying Amount		0	5
Credit facility borrowings, fair value	[2]	0	5
Term Loan
Debt Instrument [Line Items]
Long-term debt, carrying Amount	[1]	193,297	208,811
Long-term debt, fair value	[1],[2]	$ 194,250	$ 210,000

[1] Carrying amounts are net of unamortized debt issuance costs of $1.0 million as of June 30, 2025 and $1.2 million as of September 30, 2024

[2] The face amount of the Company’s variable rate long-term debt approximates fair value.