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Contents of Significant Accounts - Income Tax - Additional Information (Detail) - TWD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2023
Dec. 31, 2022
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Taxable temporary differences of unrecognized deferred tax liabilities associated with investments in subsidiaries $ 20,389 $ 21,658
Deductible temporary differences for which no deferred income tax assets have been recognized $ 3,410 $ 3,001
USJC [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Effective tax rate 27.70%  
Accounting profit $ 3,408  
UMC KOREA [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Effective tax rate 3.55%  
Accounting profit $ 2  
UME BV [Member]    
Disclosure of temporary difference, unused tax losses and unused tax credits [line items]    
Effective tax rate 20.12%  
Accounting profit $ 10