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Significant Contingent Liabilities and Unrecognized Commitments - Additional Information (Detail)
$ in Thousands, $ in Thousands
 1 Months Ended 12 Months Ended
Dec. 31, 2013
TWD ($)
Dec. 31, 2019
TWD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2018
TWD ($)
Jan. 31, 2020
TWD ($)
Jan. 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
Feb. 28, 2019
TWD ($)
Feb. 28, 2019
USD ($)
Dec. 31, 2013
USD ($)
Disclosure of contingent liabilities [line items]                    
Unused letters of credit   $ 394,000   $ 634,000     $ 13,173      
Committed to purchase property, plant and equipment   25,119,371   17,039,458     839,832      
Prepayment of property, plant and equipment   5,145,345 $ 172,028 2,339,308            
Construction contract related to real estate business   1,393,859 $ 46,602 $ 888,052            
Contractual period for environmental protection 30 years                  
Letter of credits   $ 952,001         $ 31,829      
Taiwan [member]                    
Disclosure of contingent liabilities [line items]                    
Contribution to be made for environmental protection $ 3,000,000             $ 100,000 $ 3,343 $ 100,301
Taiwan [member] | Announcing or commencing implementation of major restructuring [member]                    
Disclosure of contingent liabilities [line items]                    
Contribution to be made for environmental protection         $ 100,000 $ 3,343