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Short-Term Bank Loans - Additional Information (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Short-term Debt [Line Items]        
Proceeds from bank loan $ 50,000     $ 25,000
Repayments of bank debt 50,000   $ 25,000 $ 25,000
Interest expense $ 11 $ 0 $ 355  
Minimum        
Short-term Debt [Line Items]        
Interest rate       0.78%
Maximum        
Short-term Debt [Line Items]        
Interest rate       2.95%