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Short-term investments - Schedule of Short-Term Investments (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Schedule of Investments [Line Items]    
Short-term investments $ 117,821 $ 102,847
Time deposits [Member]    
Schedule of Investments [Line Items]    
Short-term investments 68,828 102,555
Investments in financial instruments [Member]    
Schedule of Investments [Line Items]    
Short-term investments $ 48,993 $ 292