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Property, Plant and Equipment - Additional Information (Detail)
$ in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2018
TWD ($)
Dec. 31, 2018
USD ($)
Disclosure of detailed information about property, plant and equipment [line items]    
Impairment loss recognized $ 423.5 $ 13.8
Main plants [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Estimated useful lives for property, plant and equipment 20 years 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 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 10 years
Machinery and equipment [member]    
Disclosure of detailed information about property, plant and equipment [line items]    
Impairment loss recognized $ 423.5