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)
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)			637,000
Exercise of stock options	2,156			2,156
Settlement of restricted stock units (in shares)			682,000
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	5,023			5,023
Components of other comprehensive loss:
Net income (loss)	(3,907)				(3,907)
Foreign currency translation adjustment	(2,027)						(2,027)
Unrealized gain on investments	19						19
Other comprehensive income (loss)	(5,915)
Ending Balance (in shares) at Mar. 31, 2019			39,348,000
Ending Balance at Mar. 31, 2019	98,069		$ 39	124,613	(23,989)		(2,594)
Beginning Balance (in shares) at Dec. 31, 2018			38,639,000
Beginning Balance at Dec. 31, 2018	95,568		$ 39	120,199	(23,273)		(1,397)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)			502,000
Exercise of stock options	1,570			1,570
Settlement of restricted stock units (in shares)			139,000
Settlement of restricted stock units	0
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	2,353			2,353
Components of other comprehensive loss:
Net income (loss)	(716)				(716)
Foreign currency translation adjustment	(1,203)						(1,203)
Unrealized gain on investments	6						6
Other comprehensive income (loss)	(1,913)
Ending Balance (in shares) at Mar. 31, 2019			39,348,000
Ending Balance at Mar. 31, 2019	$ 98,069		$ 39	124,613	(23,989)		(2,594)
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)	184,849		185,000
Exercise of stock options	$ 645		$ 0	645
Settlement of restricted stock units (in shares)			586,000
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	4,611			4,611
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)	1,468				1,468
Foreign currency translation adjustment	189						189
Unrealized gain on investments	58						58
Other comprehensive income (loss)	$ 1,715
Ending Balance (in shares) at Mar. 31, 2020	41,075,875		41,076,000
Ending Balance at Mar. 31, 2020	$ 113,908		$ 41	138,021	(20,340)		(3,814)
Beginning Balance (in shares) at Dec. 31, 2019			40,865,000
Beginning Balance at Dec. 31, 2019	111,524		$ 41	134,535	(20,246)		(2,806)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)			161,000
Exercise of stock options	572			572
Settlement of restricted stock units (in shares)			112,000
Settlement of restricted stock units	0
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	2,308			2,308
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)	908				908
Foreign currency translation adjustment	(1,064)						(1,064)
Unrealized gain on investments	56						56
Other comprehensive income (loss)	$ (100)
Ending Balance (in shares) at Mar. 31, 2020	41,075,875		41,076,000
Ending Balance at Mar. 31, 2020	$ 113,908		$ 41	$ 138,021	$ (20,340)		$ (3,814)