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Fair Value Information - Schedule of Impact of Decrease in Discount for Lack of Marketability or Noncontrolling Interests (Detail) - TWD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Disclosure Of Fair Value Measurement Of Financial Instruments [Abstract]    
Discount for lack of marketability, 5% increase $ (63) $ (49)
Discount for lack of marketability, 5% decrease 63 45
Noncontrolling interests discount, 5% increase (51) (22)
Noncontrolling interests discount, 5% decrease 51 22
Growth rate of long-term revenue, 0.1% increase 31 35
Growth rate of long-term revenue, 0.1% decrease (31) (35)
Discount rate, 1% increase (363) (396)
Discount rate, 1% decrease $ 439 $ 488