Income Taxes - Summary of Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Income Tax Disclosure [Abstract]
Beginning of fiscal year	$ 1,248	$ 1,216	$ 1,300
Increases in tax positions for prior years	77	50	43
Decreases in tax positions for prior years	(21)	(10)	(1)
Increases in tax positions for current year	365	146	149
Lapse of the statute of limitations	(161)	(154)	(275)
End of fiscal year	$ 1,508	$ 1,248	$ 1,216