Capital Structure and Financial Risk and Related Items - Financial liabilities (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Categories of financial liabilities recognized    
Transfers of financial liabilities from level 1 to 2 $ 0  
Transfers of financial liabilities from level 2 to 1 0  
Transfers of financial liabilities into level 3 0  
Transfers of financial liabilities from level 3 0  
Financial liabilities at amortised cost    
Categories of financial liabilities recognized    
Financial liabilities 1,203 $ 2,073
Financial liabilities, at fair value 1,203 2,073
Trade payables | Financial liabilities at amortised cost    
Categories of financial liabilities recognized    
Financial liabilities 1,203 2,073
Financial liabilities, at fair value $ 1,203 $ 2,073