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Note 6 - Shareholder's Equity - Declared Dividends (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Mar. 31, 2019	Jul. 23, 2018	Jan. 22, 2018	May 08, 2017
Per Share Dividend (in dollars per share)		$ 0.27	$ 0.25	$ 0.20
Dividend Declared May 7, 2018 [Member]
Declaration Date	May 07, 2018
Per Share Dividend (in dollars per share)	$ 0.25
Record Date	May 18, 2018
Total Amount	$ 5,150
Payment Date	May 25, 2018
Dividend Declared July 23, 2018 [Member]
Declaration Date	Jul. 23, 2018
Per Share Dividend (in dollars per share)	$ 0.27
Record Date	Aug. 03, 2018
Total Amount	$ 5,584
Payment Date	Aug. 10, 2018
Dividend Declared October 22, 2018 [Member]
Declaration Date	Oct. 22, 2018
Per Share Dividend (in dollars per share)	$ 0.27
Record Date	Nov. 05, 2018
Total Amount	$ 5,582
Payment Date	Nov. 16, 2018
Dividend Declared January 21, 2019 [Member]
Declaration Date	Jan. 21, 2019
Per Share Dividend (in dollars per share)	$ 0.27
Record Date	Feb. 04, 2019
Total Amount	$ 5,582
Payment Date	Feb. 15, 2019