Company's Debt (Detail) - USD ($) $ in Thousands		Mar. 31, 2018	Sep. 30, 2017
Debt Instrument [Line Items]
Long-term debt, carrying Amount		$ 185,838	$ 75,717
Long-term debt	[1]	60,836	65,717
Long-term debt, fair value	[2]	186,302	76,300
Long-term portion of debt, fair value	[1],[2]	61,300	66,300
Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility borrowings, carrying Amount		115,002
Credit facility borrowings, fair value	[2]	115,002
Term Loan
Debt Instrument [Line Items]
Long-term debt, carrying Amount	[1]	70,836	75,717
Long-term debt, fair value	[1],[2]	$ 71,300	$ 76,300

[1] Carrying amounts are net of unamortized debt issuance costs of $0.5 million as of March 31, 2018 and $0.6 million as of September 30, 2017.

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