Results for the year - Government grant and staff costs (Details)
$ in Thousands, € in Millions
1 Months Ended 12 Months Ended
Nov. 30, 2017
USD ($)
Dec. 31, 2017
USD ($)
segment
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2017
EUR (€)
Dec. 31, 2017
USD ($)
Disclosure of transactions between related parties [line items]            
Number of business units | segment   1        
Wages and salaries   $ 2,166 $ 2,175 $ 1,832    
Social taxes and benefits   197 407 407    
Share based payment (Note 3.4) $ 11,700 7,082 14,288 13,541    
Total employee benefits expense   9,445 16,870 15,780    
Research and development costs   5,712 9,230 6,779    
General and administrative costs   3,733 7,640 9,001    
Total   9,445 16,870 15,780    
Short term employee benefits   622 670 718    
Severance benefits   117        
Share based payment   223 3,290 5,500    
Total compensation paid to key management personnel   962 $ 3,960 $ 6,218    
FP GmbH            
Disclosure of transactions between related parties [line items]            
Government grants         € 3.8 $ 4,500
Certain members of senior management            
Disclosure of transactions between related parties [line items]            
Payment for partial repurchase of equity awards   7,200        
Amount of reversal of share-based compensation expense   $ 5,300