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Income Tax - Information About Unused Investment Credits and Loss Carryforwards (Detail)
$ in Millions, $ in Millions
Dec. 31, 2024
TWD ($)
Dec. 31, 2024
USD ($)
Dec. 31, 2023
TWD ($)
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]      
Remaining creditable amount $ 1,661 $ 51 $ 2,099
2026 [Member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]      
Remaining Creditable Amount 0   $ 8
Unused tax credits [Member] | 2026 [Member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]      
Remaining Creditable Amount 0    
Unused tax losses [Member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]      
Remaining creditable amount 73    
Unused tax losses [Member] | 2025 [Member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]      
Remaining creditable amount 17    
Unused tax losses [Member] | 2026 [Member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]      
Remaining creditable amount 10    
Unused tax losses [Member] | 2027 [Member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]      
Remaining creditable amount 3    
Unused tax losses [Member] | 2028 [Member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]      
Remaining creditable amount 1    
Unused tax losses [Member] | 2029 [Member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]      
Remaining creditable amount 2    
Unused tax losses [Member] | 2030 [Member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]      
Remaining creditable amount 1    
Unused tax losses [Member] | 2031 [Member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]      
Remaining creditable amount 1    
Unused tax losses [Member] | 2032 [Member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]      
Remaining creditable amount 6    
Unused tax losses [Member] | 2033 [Member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]      
Remaining creditable amount 20    
Unused tax losses [Member] | 2034 [Member]      
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]      
Remaining creditable amount $ 12