Note 4 - Marketable Securities - Fair Value of Marketable Securities by Maturity (Details) - USD ($)
Mar. 31, 2018
Mar. 31, 2017
Total $ 73,603,967 $ 76,402,756
Less than 1 year 20,765,809  
1-3 years 31,124,052  
3-5 years $ 21,714,106