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Operating Segments Information - Additional Information (Detail)
$ in Thousands, $ in Thousands
 12 Months Ended
Dec. 31, 2019
TWD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2018
TWD ($)
Dec. 31, 2017
TWD ($)
Disclosure of operating segments [line items]        
Operating revenue $ 413,182,184 $ 13,814,182 $ 371,092,421 $ 290,441,208
Packaging and EMS segments [member] | Customer One [member]        
Disclosure of operating segments [line items]        
Operating revenue 103,987,781 3,476,689 $ 92,117,839 $ 83,873,393
Packaging And Testing segments [member] | Customer Two [member]        
Disclosure of operating segments [line items]        
Operating revenue $ 44,653,072 $ 1,492,914