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Net Operating Loss Carryforwards available to Offset Future Taxable Income (Detail)
$ in Thousands
 12 Months Ended
Dec. 31, 2020
USD ($)
Operating Loss Carryforwards [Line Items]  
Amount $ 57,089
Hong Kong  
Operating Loss Carryforwards [Line Items]  
Amount $ 15,760
Expiring year Indefinite
Taiwan  
Operating Loss Carryforwards [Line Items]  
Amount $ 41,329
Taiwan | Earliest Tax Year  
Operating Loss Carryforwards [Line Items]  
Expiring year 2021
Taiwan | Latest Tax Year  
Operating Loss Carryforwards [Line Items]  
Expiring year 2030