Note 3 - Fair Value Measurements (Details Textual) - USD ($)	Mar. 31, 2018	Mar. 31, 2017
Fair Value, Inputs, Level 1 [Member]
Available-for-sale Securities, Total	$ 54,517,969	$ 75,098,153
Fair Value, Inputs, Level 2 [Member]
Available-for-sale Securities, Total	19,085,998	1,304,603
Fair Value, Inputs, Level 3 [Member]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0	0
Assets, Fair Value Disclosure	$ 0	$ 0