Note 11 - Share-based Compensation - Summary of Activity Relating to Company's ESPP Program (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Compensation expense	$ 43,030	$ 33,874
Shares of stock sold to employees (in shares)	33,742	43,433
Weighted average fair value per ESPP award (in dollars per share)	$ 3.94	$ 2.45

Number of shares issued during the period as a result of an employee stock purchase plan.

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