Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Sep. 30, 2018		33,813	6,385
Beginning balance at Sep. 30, 2018	$ 330,493	$ 338	$ (54,216)	$ 255,936	$ 151,961	$ (23,526)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	6,024				6,024
Other comprehensive income (loss)	(1,642)					(1,642)
Employee stock purchase plan issuances (in shares)			(63)
Employee stock purchase plan issuances	549		$ 544	5
Repurchase of common stock (in shares)			91
Repurchase of common stock	(1,044)		$ (1,044)
Issuance of stock under stock award plans (in shares)		658
Issuance of stock under stock award plans	3,751	$ 7		3,744
Stock-based compensation expense	2,707			2,707
Ending balance (in shares) at Mar. 31, 2019		34,471	6,413
Ending balance at Mar. 31, 2019	340,838	$ 345	$ (54,716)	262,392	157,985	(25,168)
Beginning balance (in shares) at Sep. 30, 2019		34,608	6,367
Beginning balance at Sep. 30, 2019	348,978	$ 346	$ (54,339)	266,567	161,919	(25,515)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,212				2,212
Other comprehensive income (loss)	176					176
Employee stock purchase plan issuances (in shares)			(53)
Employee stock purchase plan issuances	516		$ 460	56
Repurchase of common stock (in shares)			95
Repurchase of common stock	(1,684)		$ (1,684)
Issuance of stock under stock award plans (in shares)		756
Issuance of stock under stock award plans	4,724	$ 8		4,716
Stock-based compensation expense	3,441			3,441
Ending balance (in shares) at Mar. 31, 2020		35,364	6,409
Ending balance at Mar. 31, 2020	$ 358,363	$ 354	$ (55,563)	$ 274,780	$ 164,131	$ (25,339)