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Income taxes - Additional information (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Major components of tax expense income [line items]    
Deferred tax expense (income) relating to origination and reversal of temporary differences $ 39,394 $ 30,242
Tax losses 181,667 169,498
Deductible temporary differences for which deferred tax assets have not been recognized 39,394 30,242
Temporary differences associated with investments in subsidiaries 927,295 788,917
Turkey    
Major components of tax expense income [line items]    
Increase in deferred income tax expense due to exchange difference $ 12,609 $ 8,099