Condensed Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Common Stock	Treasury Stock	Accumulated Other Comprehensive Income	Accumulated Deficit	Total
Beginning balance (in shares) at Sep. 30, 2018	27,577
Common Stock, Number of Shares [Abstract]
Stock-based compensation (in shares)	305
Stock option exercises (in shares)	1
Issuance of common stock for acquisition (in shares)	811
Issuance of common stock - ESPP (in shares)	66
Ending balance (in shares) at Jun. 30, 2019	28,760
Balance, beginning of period at Sep. 30, 2018	$ 734,066		$ 885	$ (580,425)
Common Stock, Number of Shares [Abstract]
Stock-based compensation	1,824
Stock option exercises	1
Tax withholding paid on behalf of employees for stock-based awards	(203)
Issuance of common stock for acquisition	2,916
Issuance of common stock - ESPP	237
Translation adjustment			36		$ 36
Net loss				(21,009)	(21,009)
Balance, end of period at Jun. 30, 2019	$ 738,841	$ (47,721)	921	(601,434)	90,607
Beginning balance (in shares) at Mar. 31, 2019	27,856
Common Stock, Number of Shares [Abstract]
Stock-based compensation (in shares)	93
Stock option exercises (in shares)	0
Issuance of common stock for acquisition (in shares)	811
Ending balance (in shares) at Jun. 30, 2019	28,760
Balance, beginning of period at Mar. 31, 2019	$ 735,257		912	(590,957)
Common Stock, Number of Shares [Abstract]
Stock-based compensation	677
Stock option exercises	0
Tax withholding paid on behalf of employees for stock-based awards	(9)
Issuance of common stock for acquisition	2,916
Translation adjustment			9		9
Net loss				(10,477)	(10,477)
Balance, end of period at Jun. 30, 2019	$ 738,841	(47,721)	921	(601,434)	$ 90,607
Beginning balance (in shares) at Sep. 30, 2019	28,893				28,893
Common Stock, Number of Shares [Abstract]
Stock-based compensation (in shares)	283
Stock option exercises (in shares)	1
Issuance of restricted stock units (shares)					116
Issuance of common stock - ESPP (in shares)	115
Ending balance (in shares) at Jun. 30, 2020	29,408				29,408
Balance, beginning of period at Sep. 30, 2019	$ 739,926		950	(616,409)
Common Stock, Number of Shares [Abstract]
Stock-based compensation	2,625
Stock option exercises	2
Tax withholding paid on behalf of employees for stock-based awards	(82)
Issuance of restricted stock units	410
Issuance of common stock - ESPP	279
Translation adjustment			(5)		$ (5)
Net loss				(7,703)	(7,703)
Balance, end of period at Jun. 30, 2020	$ 743,160	(47,721)	945	(624,112)	$ 72,272
Beginning balance (in shares) at Mar. 31, 2020	29,291
Common Stock, Number of Shares [Abstract]
Stock-based compensation (in shares)	117
Stock option exercises (in shares)	0
Ending balance (in shares) at Jun. 30, 2020	29,408				29,408
Balance, beginning of period at Mar. 31, 2020	$ 742,416		943	(622,825)
Common Stock, Number of Shares [Abstract]
Stock-based compensation	779
Stock option exercises	0
Tax withholding paid on behalf of employees for stock-based awards	(35)
Translation adjustment			2		$ 2
Net loss				(1,287)	(1,287)
Balance, end of period at Jun. 30, 2020	$ 743,160	$ (47,721)	$ 945	$ (624,112)	$ 72,272