Annual report pursuant to Section 13 and 15(d)

Note 12 - Stock-based Compensation - Vesting Terms of Options Granted (Details) (Parentheticals)

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Note 12 - Stock-based Compensation - Vesting Terms of Options Granted (Details) (Parentheticals)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Options with Three Year Vesting [Member] | Share-based Payment Arrangement, Tranche One [Member]    
Vesting percentage 50.00% 50.00%
Options with Three Year Vesting [Member] | Share-based Payment Arrangement, Tranche Two [Member]    
Vesting percentage 25.00% 25.00%
Options with Three Year Vesting [Member] | Share-based Payment Arrangement, Tranche Three [Member]    
Vesting percentage 25.00% 25.00%
Options with Four Year Vesting [Member] | Share-based Payment Arrangement, Tranche One [Member]    
Vesting percentage 50.00% 50.00%
Options with Four Year Vesting [Member] | Share-based Payment Arrangement, Tranche Two [Member]    
Vesting percentage 16.67% 16.67%
Options with Four Year Vesting [Member] | Share-based Payment Arrangement, Tranche Three [Member]    
Vesting percentage 16.67% 16.67%
Options with Four Year Vesting [Member] | Share-based Payment Arrangement, Tranche Four [Member]    
Vesting percentage 16.67% 16.67%