CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Cumulative-effect adjustment from the adoption of ASU 2014-09	Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Deficit	Accumulated Deficit Cumulative-effect adjustment from the adoption of ASU 2014-09	Accumulated Other Comprehensive Income (Loss)
Accounting Standard Update [Extensible Enumeration]	Accounting Standards Update 2016-09 [Member]
Beginning Balance (in shares) at Sep. 30, 2018			37,961,000		0
Beginning Balance at Sep. 30, 2018	$ 95,394	$ 920	$ 38	$ 116,944	$ 0	$ (21,002)	$ 920	$ (586)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	1,384,647		1,385,000
Exercise of stock options	$ 4,500		$ 1	4,499
Settlement of restricted stock units (in shares)			881,000
Settlement of restricted stock units	0		$ 1	(1)
Issuance of common stock under employee stock purchase plan (in shares)			140,000
Issuance of common stock under employee stock purchase plan	1,081			1,081
Stock-based compensation expense	9,637			9,637
Components of other comprehensive income (loss)
Net income	(724)					(724)
Currency translation adjustment	(3,504)							(3,504)
Change in unrealized gain (loss) on investments	29							29
Other comprehensive income (loss)	(4,199)
Ending Balance (in shares) at Sep. 30, 2019			40,367,000		0
Ending Balance at Sep. 30, 2019	$ 107,333		$ 40	132,160	$ 0	(20,806)		(4,061)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	580,861		581,000
Exercise of stock options	$ 3,572		$ 1	3,571
Settlement of restricted stock units (in shares)			819,000
Settlement of restricted stock units	0		$ 1	(1)
Issuance of common stock under employee stock purchase plan (in shares)			150,000
Issuance of common stock under employee stock purchase plan	1,237			1,237
Stock-based compensation expense	9,551			9,551
Repurchase and retirements of common stock (in shares)			(137,000)
Repurchases and retirements of common stock	(1,002)					(1,002)
Components of other comprehensive income (loss)
Net income	7,814					7,814
Currency translation adjustment	3,635							3,635
Change in unrealized gain (loss) on investments	103							103
Other comprehensive income (loss)	$ 11,552
Ending Balance (in shares) at Sep. 30, 2020	41,779,853		41,780,000		0
Ending Balance at Sep. 30, 2020	$ 132,243		$ 42	146,518	$ 0	(13,994)		(323)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	329,878		330,000
Exercise of stock options	$ 2,516			2,516
Settlement of restricted stock units (in shares)			1,066,000
Settlement of restricted stock units	0		$ 1	(1)
Issuance of common stock under employee stock purchase plan (in shares)			129,000
Issuance of common stock under employee stock purchase plan	1,519			1,519
Acquisition-related shares issued (in shares)			867,000
Acquisition-related shares issued	13,943		$ 1	13,942
Stock-based compensation expense	11,532			11,532
Sale of convertible senior notes warrants	23,909			23,909
Repurchase and retirements of common stock (in shares)			(3,000)		(8,000)
Repurchases and retirements of common stock	(190)				$ (140)	(50)
Components of other comprehensive income (loss)
Net income	7,978					7,978
Currency translation adjustment	(455)							(455)
Change in unrealized gain (loss) on investments	(165)							(165)
Other comprehensive income (loss)	$ 7,358
Ending Balance (in shares) at Sep. 30, 2021	44,168,745		44,169,000		(8,000)
Ending Balance at Sep. 30, 2021	$ 192,830		$ 44	$ 199,935	$ (140)	$ (6,066)		$ (943)