Quarterly report pursuant to Section 13 or 15(d)

Stock options and restricted stock (Details)

v3.19.2
Stock options and restricted stock (Details) - USD ($)
3 Months Ended 6 Months Ended 12 Months Ended
Feb. 08, 2019
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Options exercised (in shares)       0 40,606  
Share-based compensation arrangement, exercise price         $ 474,378  
Allocated share-based compensation expense   $ 237,019 $ 223,979 $ 852,758 $ 416,180  
Antidilutive securities excluded from computation of earnings per share, amount (in shares)         36,815  
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%