Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Revision of Prior Period, Adjustment	Common Stock	Treasury Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Sep. 30, 2019			34,608,000	6,367,000
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	3,978					3,978
Other comprehensive income (loss)	(1,107)	$ 857					857
Employee stock purchase plan issuances (in shares)				(90,000)
Employee stock purchase plan issuances	798			$ 783	15
Taxes paid for net share settlement of share-based payment awards (in shares)				96,000
Taxes paid for net share settlement of share-based payment awards	(1,692)			$ (1,692)
Issuance of stock under stock award plans (in shares)			797,000
Issuance of stock under stock award plans	5,063		$ 8		5,055
Stock-based compensation expense	5,323				5,323
Ending balance (in shares) at Jun. 30, 2020			35,405,000	6,373,000
Ending balance at Jun. 30, 2020	363,305		$ 354	$ (55,248)	276,960	165,897	(24,658)
Beginning balance (in shares) at Mar. 31, 2020			35,364,000	6,410,000
Beginning balance at Mar. 31, 2020	358,363		$ 354	$ (55,563)	274,780	164,131	(25,339)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,766					1,766
Other comprehensive income (loss)	681						681
Employee stock purchase plan issuances (in shares)				(37,000)
Employee stock purchase plan issuances	283			$ 324	(41)
Taxes paid for net share settlement of share-based payment awards (in shares)				0
Taxes paid for net share settlement of share-based payment awards	(9)			$ (9)
Issuance of stock under stock award plans (in shares)			41,000
Issuance of stock under stock award plans	339		$ 0		339
Stock-based compensation expense	1,882				1,882
Ending balance (in shares) at Jun. 30, 2020			35,405,000	6,373,000
Ending balance at Jun. 30, 2020	363,305		$ 354	$ (55,248)	276,960	165,897	(24,658)
Beginning balance (in shares) at Sep. 30, 2020			35,513,000	6,353,000
Beginning balance at Sep. 30, 2020	371,500		$ 355	$ (55,109)	279,741	170,330	(23,817)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	5,778					5,778
Other comprehensive income (loss)	2,068						2,068
Issuance of common stock, net of offering expenses (in shares)			4,025,000
Issuance of common stock, net of offering expenses	73,830		$ 40		73,790
Other	8					8
Employee stock purchase plan issuances (in shares)				(61,000)
Employee stock purchase plan issuances	916			$ 540	376
Taxes paid for net share settlement of share-based payment awards (in shares)				109,000
Taxes paid for net share settlement of share-based payment awards	(1,985)			$ (1,985)
Issuance of stock under stock award plans (in shares)			974,000
Issuance of stock under stock award plans	7,025		$ 10		7,015
Stock-based compensation expense	6,331				6,331
Ending balance (in shares) at Jun. 30, 2021			40,512,000	6,401,000
Ending balance at Jun. 30, 2021	465,471		$ 405	$ (56,554)	367,253	176,116	(21,749)
Beginning balance (in shares) at Mar. 31, 2021			40,442,000	6,413,000
Beginning balance at Mar. 31, 2021	459,152		$ 404	$ (56,595)	364,604	172,951	(22,212)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	3,157					3,157
Other comprehensive income (loss)	463						463
Other	8					8
Employee stock purchase plan issuances (in shares)				(18,000)
Employee stock purchase plan issuances	297			$ 160	137
Taxes paid for net share settlement of share-based payment awards (in shares)				6,000
Taxes paid for net share settlement of share-based payment awards	(119)			$ (119)
Issuance of stock under stock award plans (in shares)			70,000
Issuance of stock under stock award plans	403		$ 1		402
Stock-based compensation expense	2,110				2,110
Ending balance (in shares) at Jun. 30, 2021			40,512,000	6,401,000
Ending balance at Jun. 30, 2021	$ 465,471		$ 405	$ (56,554)	$ 367,253	$ 176,116	$ (21,749)