Note 16 - Stock Based Compensation - Stock-based Compensation (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock based compensation expense recognized	$ 2,632,000	$ 2,116,000	$ 1,842,000
Number of unvested stock options (in shares)	2,367,515	1,962,163	1,659,102
Fair value of unvested stock options	$ 6,108,271	$ 5,550,820	$ 4,587,565
Amount remaining to be recognized as expense	$ 3,574,740	$ 3,406,394	$ 2,508,314

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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