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Note 6 - Shareholder's Equity - Declared Dividends (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Mar. 31, 2020	Jan. 21, 2020	Jul. 23, 2018	Jan. 22, 2018	May 08, 2017
Per Share Dividend (in dollars per share)		$ 0.27	$ 0.27	$ 0.25	$ 0.20
Dividend Declared May 6, 2019 [Member]
Declaration Date
Per Share Dividend (in dollars per share)	$ 0.27
Record Date	May 17, 2019
Total Amount	$ 5,518
Payment Date	May 24, 2019
Dividends Declared July 22, 2019 [Member]
Declaration Date
Per Share Dividend (in dollars per share)	$ 0.27
Record Date	Aug. 02, 2019
Total Amount	$ 5,447
Payment Date	Aug. 09, 2019
Dividends Declared October 21, 2019 [Member]
Declaration Date
Per Share Dividend (in dollars per share)	$ 0.27
Record Date	Nov. 04, 2019
Total Amount	$ 5,447
Payment Date	Nov. 15, 2019
Dividends Declared January 21, 2020 [Member]
Declaration Date
Per Share Dividend (in dollars per share)	$ 0.27
Record Date	Feb. 03, 2020
Total Amount	$ 5,445
Payment Date	Feb. 14, 2020