Note 5 - Income Taxes - Components of Income Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Current taxes
Federal	$ 9,718	$ 15,012	$ 11,095
State	1,538	1,586	1,059
Total current taxes	11,256	16,598	12,154
Deferred taxes
Federal	108	(83)	1,781
State	17	(9)	170
Total deferred taxes	125	(92)	1,951
Total provision for income taxes	$ 11,381	$ 16,506	$ 14,105