Condensed Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Treasury Stock	Accumulated other comprehensive income	Accumulated deficit
Beginning balance (in shares) at Sep. 30, 2020		29,551
Shares of common stock
Stock-based compensation (in shares)		534
Stock option exercises (in shares)		15
Issuance of common stock - ESPP (in shares)		126
Sale of common stock (in shares)		6,655
Ending balance (in shares) at Jun. 30, 2021		36,881
Balance, beginning of period at Sep. 30, 2020		$ 744,361	$ (47,721)	$ 918	$ (623,409)
Shares of common stock
Stock-based compensation		3,010
Stock option exercises		77
Tax withholding paid on behalf of employees for stock-based awards		(195)
Issuance of common stock - ESPP		382
Sale of common stock, net of offering costs		33,141
Translation adjustment	$ (26)			(26)
Net (loss) income	20,568				20,568
Balance, end of period at Jun. 30, 2021	131,106	$ 780,776	(47,721)	892	(602,841)
Beginning balance (in shares) at Mar. 31, 2021		36,775
Shares of common stock
Stock-based compensation (in shares)		101
Stock option exercises (in shares)		5
Issuance of common stock - ESPP (in shares)		0
Sale of common stock (in shares)		0
Ending balance (in shares) at Jun. 30, 2021		36,881
Balance, beginning of period at Mar. 31, 2021		$ 779,681	(47,721)	897	(616,456)
Shares of common stock
Stock-based compensation		1,176
Stock option exercises		31
Tax withholding paid on behalf of employees for stock-based awards		(112)
Issuance of common stock - ESPP		0
Sale of common stock, net of offering costs		0
Translation adjustment	(5)			(5)
Net (loss) income	13,615				13,615
Balance, end of period at Jun. 30, 2021	$ 131,106	$ 780,776	(47,721)	892	(602,841)
Beginning balance (in shares) at Sep. 30, 2021	36,984	36,984
Shares of common stock
Stock-based compensation (in shares)		553
Stock option exercises (in shares)		6
Issuance of common stock - ESPP (in shares)		0
Sale of common stock (in shares)		0
Ending balance (in shares) at Jun. 30, 2022	37,543	37,543
Balance, beginning of period at Sep. 30, 2021		$ 782,266	(47,721)	687	(597,766)
Shares of common stock
Stock-based compensation		3,755
Stock option exercises		29
Tax withholding paid on behalf of employees for stock-based awards		(307)
Issuance of common stock - ESPP		0
Sale of common stock, net of offering costs		0
Translation adjustment	$ 91			91
Net (loss) income	(7,460)				(7,460)
Balance, end of period at Jun. 30, 2022	$ 133,574	$ 785,743	(47,721)	778	(605,226)
Beginning balance (in shares) at Mar. 31, 2022		37,395
Shares of common stock
Stock-based compensation (in shares)		148
Stock option exercises (in shares)		0
Issuance of common stock - ESPP (in shares)		0
Sale of common stock (in shares)		0
Ending balance (in shares) at Jun. 30, 2022	37,543	37,543
Balance, beginning of period at Mar. 31, 2022		$ 784,371	(47,721)	709	(597,577)
Shares of common stock
Stock-based compensation		1,523
Stock option exercises		0
Tax withholding paid on behalf of employees for stock-based awards		(151)
Issuance of common stock - ESPP		0
Sale of common stock, net of offering costs		0
Translation adjustment	$ 69			69
Net (loss) income	(7,649)				(7,649)
Balance, end of period at Jun. 30, 2022	$ 133,574	$ 785,743	$ (47,721)	$ 778	$ (605,226)