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Operating Lease Arrangements - Additional Information (Detail)
$ in Thousands, $ in Thousands
 12 Months Ended
Dec. 31, 2018
USD ($)
Dec. 31, 2018
TWD ($)
Dec. 31, 2017
TWD ($)
Dec. 31, 2016
TWD ($)
Disclosure of operating lease [line items]        
Operating lease expiration 2019 to 2028 2019 to 2028    
Rental expense $ 52,052 $ 1,593,315 $ 1,193,477 $ 1,411,533
Bottom of range [member]        
Disclosure of operating lease [line items]        
Operating leasing periods 1 year 1 year    
Top of range [member]        
Disclosure of operating lease [line items]        
Operating leasing periods 15 years 15 years