Note 5 - Marketable Securities (Details Textual) - USD ($)		3 Months Ended	12 Months Ended
	Jan. 01, 2018	Mar. 31, 2018	Dec. 31, 2017
AOCI Attributable to Parent [Member]
Reclassification of Unrealized Gain (Loss) on Securities from AOCI to Retained Earnings		$ (466,025)
AOCI Attributable to Parent [Member] | Accounting Standards Update 2016-01 [Member]
Reclassification of Unrealized Gain (Loss) on Securities from AOCI to Retained Earnings	$ (466,025)
Retained Earnings [Member] | Accounting Standards Update 2016-01 [Member]
Reclassification of Unrealized Gain (Loss) on Securities from AOCI to Retained Earnings	$ 466,025