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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
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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

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