Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation - Additional Information (Details)

v3.19.1
Share-Based Compensation - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 05, 2018
Oct. 14, 2016
Oct. 14, 2015
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Mar. 14, 2018
Mar. 13, 2018
May 18, 2017
Nov. 18, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Ordinary shares, shares issued     413,110 14,352,046 413,110     413,110    
Share options granted       479,986 198,798          
Weighted average grant date fair value, options granted       $ 7.25 $ 1.91 $ 1.80        
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
Expense recognized       $ 332 $ 333          
Unamortized stock compensation expense       $ 260 $ 592          
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       $ 669 $ 59          
Vesting period       3 years 25 days 3 years 6 months 3 days          
Share options granted       479,986 198,798          
Unvested employee options outstanding       566,813 228,809          
Unamortized compensation expense share options       $ 2,822 $ 396          
Restricted Share Units (RSUs)                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Grant date fair value       $ 13.00            
Expense recognized       $ 289            
Unamortized stock compensation expense       $ 191            
Stock-based compensation expense, expected weighted average period for recognition       4 months 24 days            
Vesting period       1 year            
Number of Shares, Granted       36,924 0          
Restricted Share Units (RSUs) | Director                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Number of Shares, Granted       36,924            
Restricted Ordinary Shares, Options and Restricted Stock Units                    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                    
Vesting period       2 years 8 months 15 days 2 years 6 months 10 days          
Unamortized compensation expense       $ 3,273 $ 988          
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.