Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Accumulated Deficit [Member]
Beginning balance at Mar. 31, 2019	$ 36,298	$ 6	$ 297,047	$ 0	$ (260,755)
Beginning balance, Shares at Mar. 31, 2019		6,201,000
Issuance of common stock under employee and director stock option, RSU and purchase plans	(61)	$ 1	(62)	0	0
Issuance of common stock under employee and director stock option, RSU and purchase plans, Shares		23,000
Stock-based compensation expense	4,108	$ 0	4,108	0	0
Issuance of common stock from public offering, net	4,996	$ 0	4,996	0	0
Issuance of common stock from public offering, Shares		304,000
Net loss	(18,710)	$ 0	0	0	(18,710)
Ending balance at Mar. 31, 2020	26,631	$ 7	306,089	$ 0	(279,465)
Ending balance, Shares at Mar. 31, 2020		6,528,000		0
Stock option exercises	$ 42	$ 0	42	$ 0	0
Stock option exercises, Shares	7,800	8,000
Issuance of common stock under employee and director stock option, RSU and purchase plans	$ (4)	$ 0	(4)	0	0
Issuance of common stock under employee and director stock option, RSU and purchase plans, Shares		203,000
Stock-based compensation expense	5,556	$ 0	5,556	0	0
Issuance of common stock from public offering, net	23,798	$ 2	23,796	0	0
Issuance of common stock from public offering, Shares		1,932,000
Purchase of treasury stock	(1)	$ 0	0	$ (1)	0
Purchase of treasury stock, shares				0
Net loss	(16,826)	0	0	$ 0	(16,826)
Ending balance at Mar. 31, 2021	$ 39,196	$ 9	$ 335,479	$ (1)	$ (296,291)
Ending balance, Shares at Mar. 31, 2021		8,671,000		0