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Note 13 - Stock-based Compensation (Tables)
6 Months Ended
Jun. 30, 2021
Notes Tables  
Share-based Payment Arrangement, Option, Activity [Table Text Block]
  

Number of Shares

  

Weighted-Average Exercise Price

  

Weighted-Average of Remaining Contractual Life (in years)

  

Aggregate Intrinsic Value

 

Outstanding at December 31, 2020

  2,423,466  $4.41         

Issued

  55,000  $31.22         

Exercised

  (495,733) $3.42         

Expired/Forfeited

  (6,000) $15.30         

Outstanding at June 30, 2021

  1,976,733  $5.38   1.6  $67,851,195 

Exercisable at June 30, 2021

  1,541,401  $3.50   1.1  $55,805,456