Quarterly report pursuant to Section 13 or 15(d)

Note 4 - Stock-based Compensation (Details Textual)

v3.20.2
Note 4 - Stock-based Compensation (Details Textual) - USD ($)
1 Months Ended 3 Months Ended 6 Months Ended 9 Months Ended 18 Months Ended
Feb. 29, 2020
Jun. 30, 2020
Jun. 30, 2019
Dec. 31, 2019
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Share-based Payment Arrangement, Expense   $ 213,361 $ 433,438   $ 541,884 $ 1,535,628  
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total   2,147,356     $ 2,147,356   $ 2,147,356
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)         4 years 2 months 12 days    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)         121,350 172,000  
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)         5 years 8 months 15 days 4 years  
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)         4 years 8 months 15 days 3 years  
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price (in dollars per share)         $ 12.43 $ 12.17  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term (Year)         2 years 3 months 21 days    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value   $ 278,995     $ 278,995   $ 278,995
Proceeds from Stock Options Exercised         $ 10,968 $ 24  
Employee Stock Purchase Plan [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Market Price Percentage, Offering Date         85.00%    
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in shares)       15,107     15,116
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price (in dollars per share)       $ 11.23     $ 11.85
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized (in shares) 200,000            
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in shares)   219,623     219,623   219,623
Minimum [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)         3 years    
Maximum [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)         5 years    
Share-based Payment Arrangement, Option [Member] | Minimum [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)         3 years    
Share-based Payment Arrangement, Option [Member] | Maximum [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)         5 years    
Restricted Stock [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)         19,455    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)         $ 11.30    
Restricted Stock [Member] | Non-employee Directors [Member] | Stock Compensation Plan 2007 [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year) 1 year       1 year 1 year  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares) 5,000       5,830 4,340  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Intrinsic Value, Amount Per Share (in dollars per share) $ 11.01       $ 10.72    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)           $ 14.40  
Restricted Stock [Member] | Minimum [Member] | Employees [Member] | Stock Compensation Plan 2007 [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)         1 year    
Restricted Stock [Member] | Maximum [Member] | Employees [Member] | Stock Compensation Plan 2007 [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)         10 years    
Performance Shares [Member] | Non-employee Directors [Member] | Stock Compensation Plan 2007 [Member]              
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)         1 year    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)         8,625    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share)         $ 11.86    
Selling, General and Administrative Expenses [Member]              
Share-based Payment Arrangement, Expense   $ 207,653 410,784   $ 526,580 $ 1,450,489  
Cost of Sales [Member]              
Share-based Payment Arrangement, Expense   $ 5,708 $ 22,654   $ 15,304 $ 85,139