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Financial Instruments - Additional Information (Detail) - TWD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Disclosure of detailed information about financial instruments [Line Items] |  |  |
Sensitivity rate | 5.00% | 5.00% | 5.00%
Foreign currency risk [Member] |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |
Sensitivity rate | 5.00% | 5.00% | 5.00%
Interest rate risk [member] |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |
Sensitivity rate | 0.25% | 0.25% | 0.25%
Increase decrease in pre-tax income due to sensitivity analysis | $ 28 | $ 17 | $ 18
Equity price risk [Member] |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |
Sensitivity rate | 5.00% | 5.00% | 5.00%
Equity price risk [Member] | Pre-tax profit [Member] |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |
Increase decrease in pretax income of financial assets at FVTPL, FVOCI | $ 48 | $ 51 | $ 50
Equity price risk [Member] | Pre-tax other comprehensive income [Member] |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |
Increase decrease in pretax income of financial assets at FVTPL, FVOCI | $ 233 | $ 221 | $ 175

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