Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	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	2,212				2,212
Other comprehensive income (loss)	176					176
Employee stock purchase plan issuances (in shares)			(53,000)
Employee stock purchase plan issuances	516		$ 460	56
Taxes paid for net share settlement of share-based payment awards (in shares)			95,000
Taxes paid for net share settlement of share-based payment awards	(1,684)		$ (1,684)
Issuance of stock under stock award plans (in shares)		756,000
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		35,364,000	6,409,000
Ending balance at Mar. 31, 2020	358,363	$ 354	$ (55,563)	274,780	164,131	(25,339)
Beginning balance (in shares) at Dec. 31, 2019		35,226,000	6,431,000
Beginning balance at Dec. 31, 2019	356,315	$ 352	$ (55,702)	272,393	162,127	(22,855)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,004				2,004
Other comprehensive income (loss)	(2,484)					(2,484)
Employee stock purchase plan issuances (in shares)			(28,000)
Employee stock purchase plan issuances	230		$ 246	(16)
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	(107)		$ (107)
Issuance of stock under stock award plans (in shares)		138,000
Issuance of stock under stock award plans	564	$ 2		562
Stock-based compensation expense	1,841			1,841
Ending balance (in shares) at Mar. 31, 2020		35,364,000	6,409,000
Ending balance at Mar. 31, 2020	358,363	$ 354	$ (55,563)	274,780	164,131	(25,339)
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	2,621				2,621
Other comprehensive income (loss)	1,605					1,605
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
Employee stock purchase plan issuances (in shares)			(43,000)
Employee stock purchase plan issuances	619		$ 379	240
Taxes paid for net share settlement of share-based payment awards (in shares)			103,000
Taxes paid for net share settlement of share-based payment awards	(1,865)		$ (1,865)
Issuance of stock under stock award plans (in shares)		904,000
Issuance of stock under stock award plans	6,620	$ 9		6,611
Stock-based compensation expense	4,222			4,222
Ending balance (in shares) at Mar. 31, 2021		40,442,000	6,413,000
Ending balance at Mar. 31, 2021	459,152	$ 404	$ (56,595)	364,604	172,951	(22,212)
Beginning balance (in shares) at Dec. 31, 2020		36,090,000	6,412,000
Beginning balance at Dec. 31, 2020	377,642	$ 361	$ (56,333)	285,536	170,023	(21,945)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,928				2,928
Other comprehensive income (loss)	(267)					(267)
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
Employee stock purchase plan issuances (in shares)			(18,000)
Employee stock purchase plan issuances	285		$ 157	128
Taxes paid for net share settlement of share-based payment awards (in shares)			19,000
Taxes paid for net share settlement of share-based payment awards	(419)		$ (419)
Issuance of stock under stock award plans (in shares)		327,000
Issuance of stock under stock award plans	2,676	$ 3		2,673
Stock-based compensation expense	2,477			2,477
Ending balance (in shares) at Mar. 31, 2021		40,442,000	6,413,000
Ending balance at Mar. 31, 2021	$ 459,152	$ 404	$ (56,595)	$ 364,604	$ 172,951	$ (22,212)