Note 6 - Marketable Securities - Net Gains and Losses on Marketable Securities (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net gains (losses) recognized during the period on marketable securities	$ 86,849	$ (18,256)	$ 344,043	$ (153,406)
Less: Net (losses) gains recognized during the period on marketable securities sold during the period	(252,728)	113,276	(247,499)	113,276
Unrealized (losses) gains recognized during the reporting period on marketable securities still held at the reporting date	$ (165,879)	$ 95,020	$ 96,544	$ (40,130)