Note 9 - Fair Value Measurements (Details Textual) - USD ($)	Jun. 30, 2017	Mar. 31, 2017
Fair Value, Inputs, Level 1 [Member]
Available-for-sale Securities	$ 78,916,563	$ 75,098,153
Fair Value, Inputs, Level 2 [Member]
Available-for-sale Securities	1,294,257	1,304,603
Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure	0	0
Financial and Nonfinancial Liabilities, Fair Value Disclosure	$ 0	$ 0