v3.8.0.1
Accounting policies (Schedule of Fair Value of Financial Instruments) (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Warrant derivative liability $ 680
Recurring [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Warrant derivative liability 680  
Recurring [Member] | Level 1 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Warrant derivative liability 0  
Recurring [Member] | Level 2 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Warrant derivative liability 0  
Recurring [Member] | Level 3 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Warrant derivative liability $ 680