Long-Term Debt and Bank Facility Borrowings - Company's Debt (Detail) - USD ($) $ in Thousands		Jun. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Long-term debt, carrying Amount		$ 113,208	$ 122,805
Current maturities of long-term debt, carrying Amount		13,000	13,000
Long-term debt		100,208	109,805
Long-term debt, fair value	[1]	113,750	123,500
Current maturities of long-term debt, fair value	[1]	13,000	13,000
Long-term portion of debt, fair value	[1]	100,750	110,500
Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility borrowings, carrying Amount		0	0
Credit facility borrowings, fair value	[1]	0	0
Term Loan
Debt Instrument [Line Items]
Long-term debt, carrying Amount	[2]	113,208	122,805
Long-term debt, fair value	[1],[2]	$ 113,750	$ 123,500

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

[2] Carrying amounts are net of unamortized debt issuance costs of $0.5 million as of June 30, 2021 and $0.7 million as of September 30, 2020.