v3.21.1
Shareholders' equity - Additional paid-in capital (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Additional paid-in capital    
Opening balance $ 143,119 $ 114,917
Share-based compensation expense 1,368 981
Exercise of stock options 19 77
Closing balance 131,992 99,632
Additional paid-in capital    
Additional paid-in capital    
Opening balance 8,530 3,805
Share-based compensation expense 1,368 981
Exercise of stock options (15) (56)
Closing balance $ 9,883 $ 4,730