Company's Debt (Detail) - USD ($) $ in Thousands		Dec. 31, 2018	Sep. 30, 2018
Debt Instrument [Line Items]
Long-term debt, carrying Amount		$ 191,831	$ 100,780
Current maturities of long-term debt, carrying Amount		102,500	9,000
Long-term debt		89,331	91,780
Long-term debt, fair value	[1]	192,500	101,500
Current maturities of long-term debt, fair value	[1]	102,500	9,000
Long-term portion of debt, fair value	[1]	90,000	92,500
Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility borrowings, carrying Amount		92,500	1,500
Credit facility borrowings, fair value	[1]	92,500	1,500
Term Loan
Debt Instrument [Line Items]
Long-term debt, carrying Amount	[2]	99,331	99,280
Long-term debt, fair value	[1],[2]	$ 100,000	$ 100,000

[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 $0.7 million as of December 31, 2018 and September 30, 2018.