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Financial Risk and Fair Value Disclosures - Summary of Significant Unobservable Inputs of Fair Value Measurement in Level 3 Fair Value Hierarchy (Parenthetical) (Detail) - TWD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023
Convertible bonds [member] | Binomial Tree Valuation Model [Member] | Convertible price risk [member] | Historical volatility for shares, measurement input [member] |  |
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items] |  |
Percentage of decrease in volatility | 5.00% |
Percentage of increase in volatility | 5.00% |
Increase (decrease) in profit or loss due to percentage increase in volatility | $ (0.4) |
Increase (decrease) in profit or loss due to percentage decrease in volatility | $ 0.3 |
Embedded Derivatives In Exchangeable Bonds [member] | Binomial Tree Valuation Model [Member] | Derivative Price Risk [Member] | Historical volatility for shares, measurement input [member] |  |
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items] |  |
Percentage of decrease in volatility | 5.00% | 5.00%
Percentage of increase in volatility | 5.00% | 5.00%
Increase (decrease) in profit or loss due to percentage increase in volatility | $ (97.0) | $ (119.0)
Increase (decrease) in profit or loss due to percentage decrease in volatility | $ 113.0 | $ 131.0
Unlisted equity securities [member] | Discount for lack of marketability [member] | Market approach [member] | Equity price risk [member] |  |
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items] |  |
Percentage increase in the discount for lack of marketability | 5.00% | 5.00%
Percentage decrease in the discount for lack of marketability | 5.00% | 5.00%
Increase (decrease) in other comprehensive income due to percentage increase in the discount for lack of marketability | $ 239.0 | $ (214.0)
Increase (decrease) in other comprehensive income due to percentage decrease in the discount for lack of marketability | 239.0 | 214.0
Increase (decrease) in profit or loss due to percentage increase in the discount for lack of marketability | (309.0) | (261.0)
Increase (decrease) in profit or loss due to percentage decrease in the discount for lack of marketability | $ 244.0 | $ 199.0

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