Note 4 - Stock-based Compensation - Additional Information (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Intrinsic value of options exercised	$ 266,040	$ 2,097,888
Fair value of options vested	$ 4,131,982	$ 512,373

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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Period Type:	duration