CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Cumulative-effect adjustment from the adoption of ASU 2016-09	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Deficit Cumulative-effect adjustment from the adoption of ASU 2016-09	Accumulated Other Comprehensive Income (Loss)
Accounting Standard Update [Extensible List]	us-gaap:AccountingStandardsUpdate201609Member
Beginning Balance (in shares) at Sep. 30, 2017			33,724,000
Beginning Balance at Sep. 30, 2017	$ 61,408	$ 8,255	$ 34	$ 78,677	$ (17,450)	$ 8,255	$ 147
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	250,823		251,000
Exercise of stock options	$ 743			743
Settlement of restricted stock units (in shares)			745,000
Settlement of restricted stock units	0		$ 1	(1)
Issuance of common stock under employee stock purchase plan (in shares)			61,000
Issuance of common stock under employee stock purchase plan	382			382
Acquisition-related shares issued (in shares)			3,180,000
Acquisition-related shares issued	27,486		$ 3	27,483
Stock-based compensation expense	8,950			8,950
Amortization of closing shares and earnout shares	710			710
Components of other comprehensive loss:
Net income (loss)	(11,807)				(11,807)
Currency translation adjustment	(723)						(723)
Change in unrealized gain (loss) on investments	(10)						(10)
Other comprehensive income (loss)	(12,540)
Ending Balance (in shares) at Sep. 30, 2018			37,961,000
Ending Balance at Sep. 30, 2018	$ 95,394	$ 920	$ 38	116,944	(21,002)	$ 920	(586)
Accounting Standard Update [Extensible List]	us-gaap:AccountingStandardsUpdate201409Member
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 loss:
Net income (loss)	(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	40,367,456		40,367,000
Ending Balance at Sep. 30, 2019	$ 107,333		$ 40	132,160	(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 retirement of common stock (in shares)			(137,000)
Repurchases and retirements of common stock	(1,002)				(1,002)
Components of other comprehensive loss:
Net income (loss)	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
Ending Balance at Sep. 30, 2020	$ 132,243		$ 42	$ 146,518	$ (13,994)		$ (323)