CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Total
Beginning Balance - Shares at Mar. 31, 2017	20,612,757
Beginning Balance - Amount at Mar. 31, 2017	$ 21	$ 21,830	$ (62)	$ 64,655	$ 86,444
Issuance of common stock under employee stock option plans, shares	794,490
Issuance of common stock under employee stock option plans, amount		3,491			3,491
Stock-based compensation expense		2,070			2,070
Impact of adoption of ASU 2016-16 | ASU 2016-16				(595)	(595)
Comprehensive loss:
Net income (loss)				(4,515)	(4,515)
Net unrealized gain (loss) on available-for-sale investments			(80)		(80)
Ending Balance, Shares at Mar. 31, 2018	21,407,247
Ending Balance, Amount at Mar. 31, 2018	$ 21	27,391	(142)	59,545	86,815
Issuance of common stock under employee stock option plans, shares	933,746
Issuance of common stock under employee stock option plans, amount	$ 1	3,908			3,909
Repurchase and retirement of common stock, shares	(20,837)
Repurchase and retirement of common stock, amount		(103)			(103)
Stock-based compensation expense		2,266			2,266
Comprehensive loss:
Net income (loss)				163	163
Net unrealized gain (loss) on available-for-sale investments			105		105
Ending Balance, Shares at Mar. 31, 2019	22,320,156
Ending Balance, Amount at Mar. 31, 2019	$ 22	33,462	(37)	59,708	93,155
Issuance of common stock under employee stock option plans, shares	909,130
Issuance of common stock under employee stock option plans, amount	$ 1	4,148			4,149
Stock-based compensation expense		2,566			2,566
Comprehensive loss:
Net income (loss)				(10,337)	(10,337)
Net unrealized gain (loss) on available-for-sale investments			108		108
Ending Balance, Shares at Mar. 31, 2020	23,229,286
Ending Balance, Amount at Mar. 31, 2020	$ 23	$ 40,176	$ 71	$ 49,371	$ 89,641