Condensed Consolidated Statements of Shareholders' Equity (unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Treasury Stock	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance (in shares) at Sep. 30, 2019		28,893
Common Stock, Number of Shares [Abstract]
Stock-based compensation (in shares)		166
Stock option exercises (in shares)		1
Issuance of restricted stock units (in shares)		116
Issuance of common stock - ESPP (in shares)		115
Sale of common stock (in shares)	0
Ending balance (in shares) at Mar. 31, 2020		29,291
Balance, beginning of period at Sep. 30, 2019		$ 739,926		$ 950	$ (616,409)
Common Stock, Number of Shares [Abstract]
Stock-based compensation		1,846
Stock option exercises		2
Tax withholding paid on behalf of employees for stock-based awards		(47)
Issuance of restricted stock units		410
Issuance of common stock - ESPP		279
BOD consulting and other fees		0
Sale of common stock, net of offering costs
Translation adjustment	(7)			(7)
Net income (loss)	(6,416)				(6,416)
Balance, end of period at Mar. 31, 2020	$ 72,813	$ 742,416	$ (47,721)	943	(622,825)
Beginning balance (in shares) at Dec. 31, 2019		28,948
Common Stock, Number of Shares [Abstract]
Stock-based compensation (in shares)		111
Stock option exercises (in shares)		1
Issuance of restricted stock units (in shares)		116
Issuance of common stock - ESPP (in shares)		115
Sale of common stock (in shares)	0
Ending balance (in shares) at Mar. 31, 2020		29,291
Balance, beginning of period at Dec. 31, 2019		$ 740,680		914	(617,744)
Common Stock, Number of Shares [Abstract]
Stock-based compensation		1,045
Stock option exercises		2
Tax withholding paid on behalf of employees for stock-based awards		0
Issuance of restricted stock units		410
Issuance of common stock - ESPP		279
BOD consulting and other fees		0
Sale of common stock, net of offering costs	$ 0
Translation adjustment	29			29
Net income (loss)	(5,081)				(5,081)
Balance, end of period at Mar. 31, 2020	$ 72,813	$ 742,416	(47,721)	943	(622,825)
Beginning balance (in shares) at Sep. 30, 2020	29,551	29,551
Common Stock, Number of Shares [Abstract]
Stock-based compensation (in shares)		433
Stock option exercises (in shares)		10
Issuance of restricted stock units (in shares)		0
Issuance of common stock - ESPP (in shares)		126
Sale of common stock (in shares)	6,655
Ending balance (in shares) at Mar. 31, 2021	36,775	36,775
Balance, beginning of period at Sep. 30, 2020		$ 744,361		918	(623,409)
Common Stock, Number of Shares [Abstract]
Stock-based compensation		1,825
Stock option exercises		46
Tax withholding paid on behalf of employees for stock-based awards		(83)
Issuance of restricted stock units		0
Issuance of common stock - ESPP		382
BOD consulting and other fees		9
Sale of common stock, net of offering costs	$ 33,141
Translation adjustment	(21)			(21)
Net income (loss)	6,953				6,953
Balance, end of period at Mar. 31, 2021	$ 116,401	$ 779,681	(47,721)	897	(616,456)
Beginning balance (in shares) at Dec. 31, 2020		29,783
Common Stock, Number of Shares [Abstract]
Stock-based compensation (in shares)		203
Stock option exercises (in shares)		8
Issuance of restricted stock units (in shares)		0
Issuance of common stock - ESPP (in shares)		126
Sale of common stock (in shares)	6,655
Ending balance (in shares) at Mar. 31, 2021	36,775	36,775
Balance, beginning of period at Dec. 31, 2020		$ 745,188		908	(620,840)
Common Stock, Number of Shares [Abstract]
Stock-based compensation		922
Stock option exercises		39
Tax withholding paid on behalf of employees for stock-based awards		0
Issuance of restricted stock units		0
Issuance of common stock - ESPP		382
BOD consulting and other fees		9
Sale of common stock, net of offering costs	$ 33,141
Translation adjustment	(11)			(11)
Net income (loss)	4,384				4,384
Balance, end of period at Mar. 31, 2021	$ 116,401	$ 779,681	$ (47,721)	$ 897	$ (616,456)