v3.26.1
Financial Risk and Fair Value Disclosures - Additional Information (Detail) - TWD ($)
$ in Millions
12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Accounts receivables from the top ten customers 61.00% 66.00%  
Profit or loss attributable to change in unrealized gains or losses for financial assets without quoted market prices held at end of period $ (311) $ 128 $ (1,329)
Profit or loss attributable to change in unrealized gains or losses for financial liabilities without quoted market prices held at end of period 845 119 (581)
Interest rate risk [member]      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Increase (decrease) in profit due to percentage increase in market risk (23) (45) (36)
Increase (decrease) in profit due to percentage decrease in market risk $ 23 $ 45 $ 36
Equity price risk [member]      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Percentage increase in market risk 5.00% 5.00% 5.00%
Increase (decrease) in profit due to percentage increase in market risk $ 268 $ 261 $ 270
Percentage decrease in market risk 5.00% 5.00% 5.00%
Increase (decrease) in profit due to percentage decrease in market risk $ (268) $ (261) $ (270)
Increase (decrease) in other comprehensive income due to percentage increase in market risk 531 689 722
Increase (decrease) in other comprehensive income due to percentage decrease in market risk $ (531) $ (689) $ (722)
Taiwan, New Dollars [member] | Currency risk [member]      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Percentage increase in market risk 10.00% 10.00% 10.00%
Increase (decrease) in profit due to percentage increase in market risk $ (534) $ (1,095) $ (620)
Percentage decrease in market risk 10.00% 10.00% 10.00%
Increase (decrease) in profit due to percentage decrease in market risk $ 534 $ 1,095 $ 620
China, Yuan Renminbi [member] | Currency risk [member]      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Percentage increase in market risk 10.00% 10.00% 10.00%
Increase (decrease) in profit due to percentage increase in market risk $ (175) $ (615) $ (582)
Percentage decrease in market risk 10.00% 10.00% 10.00%
Increase (decrease) in profit due to percentage decrease in market risk $ 175 $ 615 $ 582
Japan, Yen [member] | Currency risk [member]      
Disclosure of nature and extent of risks arising from financial instruments [line items]      
Percentage increase in market risk 10.00% 10.00% 10.00%
Increase (decrease) in profit due to percentage increase in market risk $ (206) $ (237) $ (290)
Percentage decrease in market risk 10.00% 10.00% 10.00%
Increase (decrease) in profit due to percentage decrease in market risk $ 206 $ 237 $ 290