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Financial Instruments - Foreign Currency Risk Sensitivity Analysis (Detail) - TWD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Profit and loss [Member] | Financial instruments [Member] | USD [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	$ 87	$ 51	$ 75
Profit and loss [Member] | Financial instruments [Member] | EUR [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	(49)	(30)	(39)
Profit and loss [Member] | Financial instruments [Member] | SGD [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	(33)	(47)	(69)
Profit and loss [Member] | Financial instruments [Member] | RMB [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	7	6	0
Profit and loss [Member] | Derivatives [Member] | USD [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	2	0	0
Profit and loss [Member] | Derivatives [Member] | EUR [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	1	7	3
Equity [Member] | Derivatives [Member] | EUR [Member]
Disclosure of detailed information about financial instruments [Line Items]
Sensitivity analysis due to a 5% increase or decrease in foreign currency exchange	$ 17	$ 1	$ 22

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