Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation - Additional Information (Details)

v3.20.4
Share-Based Compensation - Additional Information (Details) - USD ($)
12 Months Ended
Feb. 14, 2020
Dec. 05, 2018
Oct. 14, 2016
Oct. 14, 2015
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Jun. 10, 2020
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 49,431,028 14,868,973       413,110    
Share options granted         64,840 512,778 479,986          
Weighted average grant date fair value, options granted         $ 1.28 $ 3.80 $ 7.25          
Restricted Ordinary Shares                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Shares issued in the period       413,110 0              
Percentage of remaining restricted ordinary shares vest on monthly basis     0.0278%                  
Grant date fair value                       $ 3.14
Expense recognized           $ 260,000 $ 332,000          
Unamortized stock compensation expense         $ 0 0 $ 260,000          
Stock-based compensation expense, expected weighted average period for recognition             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         $ 1,136,000 $ 1,388,000 $ 669,000          
Vesting period         1 year 5 months 19 days 2 years 7 months 9 days 3 years 25 days          
Share options granted         64,840 512,778 479,986          
Unvested employee options outstanding         266,666 837,386 479,986          
Unamortized compensation expense share options         $ 970,000 $ 3,342,000 $ 2,822,000          
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         63,000 $ 313,000            
Unamortized stock compensation expense         $ 0 $ 99,000            
Stock-based compensation expense, expected weighted average period for recognition           5 months 12 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         0 31,367 36,924          
Performance RSUs                        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]                        
Grant date fair value         $ 1.99 $ 8.21            
Expense recognized         $ 1,560,000 $ 212,000            
Unamortized stock compensation expense         $ 152,000 $ 198,000            
Stock-based compensation expense, expected weighted average period for recognition         2 months 12 days 9 months 21 days            
Number of shares, granted/awarded         1,079,000 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         9 months 18 days 2 years 5 months 8 days 2 years 8 months 15 days          
Unamortized compensation expense         $ 1,122,000 $ 3,639,000 $ 3,273,000          
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% 4.00%                    
Ordinary shares, shares issued 594,758           574,081 2,250,000        
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.