Stock-based Compensation Plans - Stock option activity (Details)
9 Months Ended
Sep. 30, 2020
USD ($)
$ / shares
shares
Sep. 30, 2020
USD ($)
$ / shares
shares
Weighted Average Exercise Price    
Weighted Average Remaining Contractual Term, options vested and expected to vest 3 years 1 month 6 days 3 years
Stock options    
Number of shares    
Outstanding at beginning of year | shares   93,488
Granted | shares   0
Exercise | shares   0
Forfeited or expired | shares   0
Outstanding at end of period | shares 93,488 93,488
Vested and expected to vest | shares 93,488 93,488
Exercisable at end of period | shares 23,429 23,429
Weighted Average Exercise Price    
Outstanding at beginning of year | $ / shares   $ 13.17
Granted | $ / shares   0.00
Exercise | $ / shares   0.00
Forfeited or expired | $ / shares   0.00
Outstanding at end of period | $ / shares $ 13.17 13.17
Vested and expected to vest | $ / shares 13.17 13.17
Exercisable at end of period | $ / shares $ 12.65 $ 12.65
Weighted Average Remaining Contractual Term   9 years 1 month 6 days
Weighted Average Remaining Contractual Term, options vested and expected to vest   9 years 1 month 6 days
Weighted Average Remaining Contractual Term, options exercisable   8 years 7 months 6 days
Outstanding shares, Aggregate Intrinsic Value | $ $ 15,000 $ 15,000
Vested and expected to vest, Aggregate Intrinsic Value | $ 15,000 15,000
Exercisable at end of period Aggregate Intrinsic Value | $ $ 15,000 $ 15,000