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Property, Plant and Equipment - Additional Information (Detail) - TWD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Mar. 31, 2021
Jun. 30, 2021
Jun. 30, 2020
Bottom of range [member]      
Disclosure of detailed information about property, plant and equipment [line items]      
Operating lease term   1 year 1 year
Top of range [member]      
Disclosure of detailed information about property, plant and equipment [line items]      
Operating lease term   5 years 5 years
Main plants [member]      
Disclosure of detailed information about property, plant and equipment [line items]      
Estimated useful lives for property, plant and equipment   20 years  
Mechanical and electrical power equipment [member]      
Disclosure of detailed information about property, plant and equipment [line items]      
Estimated useful lives for property, plant and equipment   10 years  
Clean rooms [member]      
Disclosure of detailed information about property, plant and equipment [line items]      
Estimated useful lives for property, plant and equipment   10 years  
Machinery and equipment      
Disclosure of detailed information about property, plant and equipment [line items]      
Reversal of impairment $ 274.4