Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands		Total		Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings		Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment from adoption of new accounting policy | ASU 2014-09		$ (152)					$ (152)	[1]
Beginning balance at Sep. 30, 2016		300,029		$ 325	$ (54,209)	$ 237,492	141,112	[1]	$ (24,691)
Beginning balance (in shares) at Sep. 30, 2016				32,471	6,431
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	[1]	9,403					9,403
Net income | ASU 2014-09		9,403
Other comprehensive income (loss)		2,032	[1]						2,032
Employee stock purchase issuances (in shares)					(72)
Employee stock purchase issuances		685			$ 614	71
Repurchase of common stock (in shares)					78
Repurchase of common stock		(938)			$ (938)
Issuance of stock under stock award plans (in shares)				537
Issuance of stock under stock award plans		3,502		$ 5		3,497
Tax impact from equity awards		(191)				(191)
Stock-based compensation expense		4,659				4,659
Ending balance (in shares) at Sep. 30, 2017				33,008	6,437
Ending balance at Sep. 30, 2017		319,029		$ 330	$ (54,533)	245,528	150,363	[1]	(22,659)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment from adoption of new accounting policy | ASU 2016-09		19				52	(33)	[1]
Net income	[1]	1,631					1,631
Net income | ASU 2014-09		1,631
Other comprehensive income (loss)		(867)	[1]						(867)
Employee stock purchase issuances (in shares)					(126)
Employee stock purchase issuances		1,115			$ 1,065	50
Repurchase of common stock (in shares)					74
Repurchase of common stock		(748)			$ (748)
Issuance of stock under stock award plans (in shares)				805
Issuance of stock under stock award plans		5,460		$ 8		5,452
Stock-based compensation expense		4,854				4,854
Ending balance (in shares) at Sep. 30, 2018				33,813	6,385
Ending balance at Sep. 30, 2018		330,493	[1]	$ 338	$ (54,216)	255,936	151,961	[1]	(23,526)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		9,958					9,958	[1]
Other comprehensive income (loss)		(1,989)							(1,989)
Employee stock purchase issuances (in shares)					(111)
Employee stock purchase issuances		1,058			$ 948	110
Repurchase of common stock (in shares)					93
Repurchase of common stock		(1,071)			$ (1,071)
Issuance of stock under stock award plans (in shares)				795
Issuance of stock under stock award plans		4,874		$ 8		4,866
Stock-based compensation expense		5,655				5,655
Ending balance (in shares) at Sep. 30, 2019				34,608	6,367
Ending balance at Sep. 30, 2019		$ 348,978		$ 346	$ (54,339)	$ 266,567	$ 161,919	[1]	$ (25,515)

[1] Prior period information has been restated for the adoption of ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606)”, which we adopted on October 1, 2018.