Results for the year - Net income (loss) per share (Details) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Results for the year      
Annulment of ordinary shares (as a percent) 80.00%    
Premium (as a percent) 15.00%    
Share split (ratio) 11.5    
Net income (loss) attributable to ordinary shareholders of the Parent used for computing basic and diluted net income (loss) per share $ 917,093 $ (33,336) $ (37,004)
Weighted average number of ordinary shares used for basic per share amounts 380,133 540,650 537,614
Dilutive effect of outstanding options, warrants and deferred shares 18,810    
Weighted average number of ordinary shares used for diluted per share amounts 398,943 540,650 537,614
Net income (loss) per share basic $ 2.41 $ (0.06) $ (0.07)
Net income (loss) per share diluted $ 2.30 $ (0.06) $ (0.07)
Anti-dilutive securities 8,200 50,400 47,400