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Financial Assets at Fair Value Through Other Comprehensive Income - Additional Information (Detail)
$ in Thousands, $ in Thousands
 12 Months Ended
Dec. 31, 2020
TWD ($)
Bonds
Dec. 31, 2020
USD ($)
Dec. 31, 2019
TWD ($)
Dec. 31, 2019
USD ($)
Financial assets at fair value through other comprehensive income [line items]        
Unsecured subordinate corporate bonds amount $ 1,082,000 $ 38,533 $ 1,325,327  
Unsecured subordinate corporate bonds [member]        
Financial assets at fair value through other comprehensive income [line items]        
Unsecured subordinate corporate bonds amount $ 1,000,000 $ 36 $ 1,000 $ 36
Number of bonds acquired 1,000      
Corporate bonds annual interest rate 3.50% 3.50% 3.50% 3.50%
Effective interest rate 3.20% 3.20% 3.20% 3.20%