Note 6 - Marketable Securities - Summary of Investments (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Debt securities, cost	$ 4,703,762	$ 3,742,681
Debt securities	4,703,762	3,742,681
Equity securities, cost	2,639,011	3,626,952
Equity securities	2,988,118	3,879,515
Equity securities, unrealized gain	349,107	252,563
Marketable securities, cost	7,342,773	7,369,633
Marketable securities	7,691,880	7,622,196
Marketable securities, unrealized gain	349,107	252,563
US Treasury Securities [Member]
Debt securities, cost	4,703,762	3,742,681
Debt securities	4,703,762	3,742,681
Fixed Income Securities [Member]
Equity securities, cost	2,037,031	2,408,799
Equity securities	2,182,337	2,409,213
Equity securities, unrealized gain	145,306	414
Equity And Other Mutual Funds [Member]
Equity securities, cost	601,980	1,218,153
Equity securities	805,781	1,470,302
Equity securities, unrealized gain	$ 203,801	$ 252,149