Income Taxes - Schedule of Reconciliation Difference of Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Amount at statutory U.S. federal income tax rate	$ 2,461	$ 5,932	$ 6,385
Change because of the following items:
State income taxes, net of federal benefit	(13)	142	67
Stock-based compensation	330	(607)	16
Valuation allowance change	665	(2,500)	348
Tax reserve change	(52)	258	34
Federal manufacturing deduction	(313)	(280)	(268)
U.S. Federal and foreign research and development credits	(706)	(571)	(74)
Gain on strategic investment and corporate subsidiary		2,630
Foreign rate differential	948	622
Acquisition-related transaction costs		768
Contingent consideration (gain) expense	(45)	522
Unrealized foreign currency exchange loss on contingent consideration obligation	170
Other	(338)	47	(214)
Income tax provision	$ 3,107	$ 6,963	$ 6,294