Condensed Consolidated Statement of Stockholders' Equity (Unaudited) - 9 months ended Jun. 30, 2017 - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Beginning Balance at Sep. 30, 2016	$ 312,473	$ 26	$ 241,058	$ 103,212	$ (31,823)
Beginning Balance, Shares at Sep. 30, 2016	25,977,632	25,977,632
Net income	$ 19,636			19,636
Purchase of treasury stock	(4,919)				(4,919)
Shares issued pursuant to employee stock purchase plan	887		887
Shares issued pursuant to employee stock purchase plan, Shares		51,697
Shares issued upon vesting of equity awards, net of minimum tax withholding	(87)		(87)
Shares issued upon vesting of equity awards, net of minimum tax withholding, Shares		9,087
Shares issued upon exercise of stock options	2,142		2,142
Shares issued upon exercise of stock options, Shares		175,431
Stock-based compensation	4,600		4,600
Stock-based compensation, Shares		40,992
Ending Balance at Jun. 30, 2017	$ 334,732	$ 26	$ 248,600	$ 122,848	$ (36,742)
Ending Balance, Shares at Jun. 30, 2017	26,254,839	26,254,839