Quarterly report pursuant to Section 13 or 15(d)

Stock options and restricted stock (Details)

v3.19.3
Stock options and restricted stock (Details) - USD ($)
3 Months Ended 9 Months Ended 12 Months Ended
Feb. 08, 2019
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Options exercised (in shares)       0 85,440  
Share-based compensation arrangement, exercise price         $ 1,033,108  
Cashless exercises         $ 891,255  
Antidilutive securities excluded from computation of earnings per share, amount (in shares)         600  
2016 Performance Stock Awards Plan            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Vesting period           3 years
Equity instruments other options, grants in period (in shares) 46,477          
Equity instruments other than options, grants in period, weighted average grant date fair value (in dollars per share) $ 8.05          
2016 Performance Stock Awards Plan | Minimum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percentage of target award           0.00%
2016 Performance Stock Awards Plan | Maximum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Percentage of target award           150.00%
2015 Stock Awards Plan            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Equity instruments other options, grants in period (in shares) 44,949          
Equity instruments other than options, grants in period, weighted average grant date fair value (in dollars per share) $ 15.72          
Period after option grant before options can be exercised (in years) 1 year          
2015 Stock Awards Plan | Minimum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Annual vesting rate (percent) 20.00%          
2015 Stock Awards Plan | Maximum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Annual vesting rate (percent) 33.00%          
Capital in Excess of Par Value            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Employee stock compensation   $ 907,698 $ (205,520) $ 1,760,456 $ (621,699)