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Retirement Benefit Plans - Additional Information (Detail)
$ in Thousands, $ in Thousands
 12 Months Ended
Dec. 31, 2019
TWD ($)
Unit
Dec. 31, 2019
USD ($)
Unit
Dec. 31, 2018
TWD ($)
Disclosure of defined benefit plans [Line Items]      
Defined benefit plans expected contribution $ 27,337 $ 0  
Weighted average duration of defined benefit obligation 12 years 9 months 18 days 12 years 9 months 18 days  
Defined benefit pension plan [Member]      
Disclosure of defined benefit plans [Line Items]      
Number of units accrued in first tranche 2 2  
Duration of first tranche First 15 years First 15 years  
Number of units accrued in second tranche 1 1  
Duration of second tranche Thereafter 15 years Thereafter 15 years  
Maximum number of units accruable under the pension plan 45 45  
Benefit measurement period 6 months 6 months  
Employer contribution percentage 2.00% 2.00%  
Defined contribution pension plan [member]      
Disclosure of defined benefit plans [Line Items]      
Employer contribution percentage 6.00% 6.00% 6.00%
Pension costs under defined contribution pension plans | $ $ 187,502   $ 193,047