Company's Debt (Detail) - USD ($) $ in Thousands		Dec. 31, 2017	Sep. 30, 2017
Debt Instrument [Line Items]
Long-term debt, carrying Amount		$ 152,427	$ 75,717
Long-term debt	[1]	63,278	65,717
Long-term debt, fair value	[2]	152,949	76,300
Long-term portion of debt, fair value	[1],[2]	63,800	66,300
Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt, carrying Amount		79,149
Long-term debt, fair value	[2]	79,149
Term Loan
Debt Instrument [Line Items]
Long-term debt, carrying Amount	[1]	73,278	75,717
Long-term debt, fair value	[1],[2]	$ 73,800	$ 76,300

[1] Carrying amounts are net of unamortized debt issuance costs of $0.5 million as December 31, 2017 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.