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Fair value measurements - Schedule of financial instruments measured at fair value (Detail) - USD ($)
$ in Thousands
Dec. 31, 2021
Dec. 31, 2020
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]    
Total $ 53,273 $ 48,993
Investments in financial instruments [Member]    
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]    
Investments in structured deposits and wealth management products 53,273 48,993
Significant other observable inputs (Level 2) [Member]    
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]    
Total 53,273 48,993
Significant other observable inputs (Level 2) [Member] | Investments in financial instruments [Member]    
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]    
Investments in structured deposits and wealth management products $ 53,273 $ 48,993