Note 7 - Income Taxes - Schedule of Income Tax Provisions (Details) - USD ($)	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Current taxes
Federal, Current taxes	$ 5,899,574	$ 6,034,924	$ 5,754,428
State, Current taxes	160,670	138,689	186,822
Deferred taxes
Federal, Deferred taxes	31,800	(25,196)	(55,254)
State, Deferred taxes	4,108	(1,275)	(1,214)
Income tax provision	$ 6,096,152	$ 6,147,142	$ 5,884,782