v3.8.0.1
Accounting policies (Schedule of Assumptions Used to Value Convertible Notes) (Details) - $ / shares
12 Months Ended
Apr. 05, 2017
Dec. 31, 2017
Nov. 13, 2017
Mar. 20, 2017
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]        
Market price per share (USD/share) $ 2.75 $ 1.06 $ 1.20 $ 2.85
Exercise price (USD/share) $ 2.75 $ 1.00    
Risk-free rate 1.83% 2.00%    
Dividend yield 0.00% 0.00%    
Expected term/Contractual life (years) 4 years 3 years 3 months 4 days    
Expected volatility 106.46% 110.46%