Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation - Additional Information (Details)

v3.20.1
Share-Based Compensation - Additional Information (Details) - USD ($)
12 Months Ended
Dec. 05, 2018
Oct. 14, 2016
Oct. 14, 2015
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Mar. 14, 2018
Mar. 13, 2018
May 18, 2017
Dec. 31, 2016
Nov. 18, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Ordinary shares, shares issued     413,110 14,868,973 14,352,046     413,110      
Share options granted       512,778 479,986 198,798          
Weighted average grant date fair value, options granted       $ 3.80 $ 7.25 $ 1.91          
Restricted Ordinary Shares                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Shares issued in the period     413,110                
Percentage of remaining restricted ordinary shares vest on monthly basis   0.0278%                  
Grant date fair value       $ 3.14 $ 3.14 $ 3.14       $ 3.14 $ 3.14
Expense recognized       $ 260,000 $ 332,000 $ 333,000          
Unamortized stock compensation expense       $ 0 $ 260,000 $ 592,000          
Stock-based compensation expense, expected weighted average period for recognition         9 months 14 days 1 year 9 months 14 days          
Restricted Ordinary Shares | Tranche One                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Percentage of awards vested   25.00%                  
Employee Stock Options                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Risk-free interest rate based on estimate of U.S. treasury yield       7 years              
Employees and Directors                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Expense recognized       $ 1,388,000 $ 669,000 $ 59,000          
Vesting period       2 years 7 months 9 days 3 years 25 days 3 years 6 months 3 days          
Share options granted       512,778 479,986 198,798          
Unvested employee options outstanding       837,386 566,813 228,809          
Unamortized compensation expense share options       $ 3,342,000 $ 2,822,000 $ 396,000          
Restricted Share Units (RSUs)                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Grant date fair value       $ 7.01 $ 13.00            
Expense recognized       $ 313,000 $ 289,000            
Unamortized stock compensation expense       $ 99,000 $ 191,000            
Stock-based compensation expense, expected weighted average period for recognition       5 months 12 days 4 months 24 days            
Number of shares, granted/awarded       31,367 36,924            
Restricted Share Units (RSUs) | Director                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Vesting period       1 year              
Number of shares, granted/awarded       31,367 36,924 0          
Performance RSUs                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Grant date fair value       $ 8.21              
Expense recognized       $ 212,000              
Unamortized stock compensation expense       $ 198,000              
Stock-based compensation expense, expected weighted average period for recognition       9 months 21 days              
Number of shares, granted/awarded       50,000 0            
Restricted Ordinary Shares, Options and Restricted Share Units and Performance Restricted Share Units                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Vesting period       2 years 5 months 8 days 2 years 8 months 15 days 2 years 6 months 10 days          
Unamortized compensation expense       $ 3,639,000 $ 3,273,000 $ 988,000          
2015 Plan                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Number of shares authorized                     223,424
Number of ordinary shares available for issuance                 443,029   219,605
2018 Plan                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Number of shares authorized             1,018,459        
Increase in number of ordinary shares available to be granted, percentage 4.00%                    
Ordinary shares, shares issued         574,081            
2015 Plan and 2018 Plan | Employee Stock Options                      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                      
Share option granted term       10 years              
Vesting period       4 years              
Vesting rights       The vesting requirement is conditioned upon a grantee’s continued service with the Company during the vesting period. Once vested, all awards are exercisable from the date of grant until they expire. The option grants are non-transferable. Vested options generally remain exercisable for 90 days subsequent to the termination of the option holder’s service with the Company. In the event of an option holder’s disability or death while employed by or providing service to the Company, the exercisable period extends to twelve months or eighteen months, respectively.