Note 3 - Net Income Per Share - Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020
Net income (numerator):
Net income	$ 4,257	$ 7,611	$ 15,034	$ 23,791
Shares (denominator):
Weighted average number of common shares outstanding used in basic computation (in shares)	20,208	20,094	20,165	20,047
Common shares issuable upon vesting of restricted stock (in shares)	111	0	190	43
Common shares issuable upon conversion of preferred shares (in shares)	10	10	10	10
Shares used in diluted computation (in shares)	20,329	20,104	20,365	20,100
Net income per common share:
Basic (in USD per Share)	$ 0.21	$ 0.38	$ 0.75	$ 1.19
Diluted (in USD per Share)	$ 0.21	$ 0.38	$ 0.74	$ 1.18