CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning Balance (in shares) at Sep. 30, 2017		33,724,000
Beginning Balance at Sep. 30, 2017	$ 61,408	$ 34	$ 78,677	$ (17,450)	$ 147
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		73,000
Exercise of stock options	166		166
Settlement of restricted stock units (in shares)		596,000
Settlement of restricted stock units	0
Acquisition-related shares issued (in shares)		666,000
Acquisition-related shares issued	5,610	$ 1	5,609
Stock-based compensation expense	3,947		3,947
Amortization of earnout shares	710		710
Components of other comprehensive loss:
Net loss	(6,896)			(6,896)
Foreign currency translation adjustment	592				592
Unrealized gain (loss) on investments	(71)				(71)
Other comprehensive loss	(6,375)
Ending Balance (in shares) at Mar. 31, 2018		35,059,000
Ending Balance at Mar. 31, 2018	73,721	$ 35	89,109	(16,091)	668
Beginning Balance (in shares) at Dec. 31, 2017		34,903,000
Beginning Balance at Dec. 31, 2017	72,401	$ 35	87,020	(14,931)	277
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		9,000
Exercise of stock options	31		31
Settlement of restricted stock units (in shares)		147,000
Settlement of restricted stock units	0
Stock-based compensation expense	2,058		2,058
Components of other comprehensive loss:
Net loss	(1,160)			(1,160)
Foreign currency translation adjustment	403				403
Unrealized gain (loss) on investments	(12)				(12)
Other comprehensive loss	(769)
Ending Balance (in shares) at Mar. 31, 2018		35,059,000
Ending Balance at Mar. 31, 2018	$ 73,721	$ 35	89,109	(16,091)	668
Beginning Balance (in shares) at Sep. 30, 2018	37,961,224	37,961,000
Beginning Balance at Sep. 30, 2018	$ 95,394	$ 38	116,944	(21,002)	(586)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	637,051	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 stock purchase plan	491		491
Stock-based compensation expense	5,023		5,023
Components of other comprehensive loss:
Net loss	(3,907)			(3,907)
Foreign currency translation adjustment	(2,027)				(2,027)
Unrealized gain (loss) on investments	19				19
Other comprehensive loss	$ (5,915)
Ending Balance (in shares) at Mar. 31, 2019	39,348,080	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
Issuance of common stock under employee stock purchase plan (in shares)		68,000
Issuance of common stock under employee stock purchase plan	491		491
Stock-based compensation expense	2,353		2,353
Components of other comprehensive loss:
Net loss	(716)			(716)
Foreign currency translation adjustment	(1,203)				(1,203)
Unrealized gain (loss) on investments	6				6
Other comprehensive loss	$ (1,913)
Ending Balance (in shares) at Mar. 31, 2019	39,348,080	39,348,000
Ending Balance at Mar. 31, 2019	$ 98,069	$ 39	$ 124,613	$ (23,989)	$ (2,594)