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	4,682				4,682
Other comprehensive income (loss)	(1,566)					(1,566)
Employee stock purchase plan issuances (in shares)			(33)
Employee stock purchase plan issuances	289		$ 288	1
Repurchase of common stock (in shares)			84
Repurchase of common stock	(964)		$ (964)
Issuance of stock under stock award plans (in shares)		263
Issuance of stock under stock award plans	662	$ 3		659
Stock-based compensation expense	1,414			1,414
Ending balance (in shares) at Dec. 31, 2018		34,076	6,436
Ending balance at Dec. 31, 2018	335,010	$ 341	$ (54,892)	258,010	156,643	(25,092)
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	208				208
Other comprehensive income (loss)	2,660					2,660
Employee stock purchase plan issuances (in shares)			(25)
Employee stock purchase plan issuances	286		$ 214	72
Repurchase of common stock (in shares)			89
Repurchase of common stock	(1,577)		$ (1,577)
Issuance of stock under stock award plans (in shares)		618
Issuance of stock under stock award plans	4,160	$ 6		4,154
Stock-based compensation expense	1,600			1,600
Ending balance (in shares) at Dec. 31, 2019		35,226	6,431
Ending balance at Dec. 31, 2019	$ 356,315	$ 352	$ (55,702)	$ 272,393	$ 162,127	$ (22,855)