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	Accumulated Deficit	Accumulated Deficit Cumulative-effect adjustment from the adoption of ASU 2014-09	Accumulated Other Comprehensive Income (Loss)
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201409Member
Beginning Balance (in shares) at Sep. 30, 2018			37,961,000
Beginning Balance at Sep. 30, 2018	$ 95,394	$ 920	$ 38	$ 116,944	$ (21,002)	$ 920	$ (586)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)			1,362,000
Exercise of stock options	4,421		$ 1	4,420
Settlement of restricted stock units (in shares)			786,000
Settlement of restricted stock units	0		$ 1	(1)
Issuance of common stock under employee stock purchase plan (in shares)			68,000
Issuance of common stock under employee purchase plan	491			491
Stock-based compensation expense	7,291			7,291
Components of other comprehensive loss:
Net income (loss)	(4,006)				(4,006)
Foreign currency translation adjustment	(1,213)						(1,213)
Unrealized gain on investments	26						26
Other comprehensive income (loss)	(5,193)
Ending Balance (in shares) at Jun. 30, 2019			40,177,000
Ending Balance at Jun. 30, 2019	103,324		$ 40	129,145	(24,088)		(1,773)
Beginning Balance (in shares) at Mar. 31, 2019			39,348,000
Beginning Balance at Mar. 31, 2019	98,069		$ 39	124,613	(23,989)		(2,594)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)			726,000
Exercise of stock options	2,265		$ 1	2,264
Settlement of restricted stock units (in shares)			103,000
Settlement of restricted stock units	0
Stock-based compensation expense	2,268			2,268
Components of other comprehensive loss:
Net income (loss)	(99)				(99)
Foreign currency translation adjustment	814						814
Unrealized gain on investments	7						7
Other comprehensive income (loss)	722
Ending Balance (in shares) at Jun. 30, 2019			40,177,000
Ending Balance at Jun. 30, 2019	$ 103,324		$ 40	129,145	(24,088)		(1,773)
Beginning Balance (in shares) at Sep. 30, 2019	40,367,456		40,367,000
Beginning 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)	301,060		301,000
Exercise of stock options	$ 1,038			1,038
Settlement of restricted stock units (in shares)			677,000
Settlement of restricted stock units	0		$ 1	(1)
Issuance of common stock under employee stock purchase plan (in shares)			75,000
Issuance of common stock under employee purchase plan	606			606
Stock-based compensation expense	7,112			7,112
Repurchases and retirements 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)	2,816				2,816
Foreign currency translation adjustment	1,324						1,324
Unrealized gain on investments	156						156
Other comprehensive income (loss)	$ 4,296
Ending Balance (in shares) at Jun. 30, 2020	41,282,779		41,283,000
Ending Balance at Jun. 30, 2020	$ 119,383		$ 41	140,915	(18,992)		(2,581)
Beginning Balance (in shares) at Mar. 31, 2020			41,076,000
Beginning Balance at Mar. 31, 2020	113,908		$ 41	138,021	(20,340)		(3,814)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)			116,000
Exercise of stock options	393			393
Settlement of restricted stock units (in shares)			91,000
Settlement of restricted stock units	0
Stock-based compensation expense	2,501			2,501
Components of other comprehensive loss:
Net income (loss)	1,348				1,348
Foreign currency translation adjustment	1,135						1,135
Unrealized gain on investments	98						98
Other comprehensive income (loss)	$ 2,581
Ending Balance (in shares) at Jun. 30, 2020	41,282,779		41,283,000
Ending Balance at Jun. 30, 2020	$ 119,383		$ 41	$ 140,915	$ (18,992)		$ (2,581)