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Financial Risk and Fair Value Disclosures - Additional Information (Detail) - TWD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disclosure of nature and extent of risks arising from financial instruments [line items]
Accounts receivables from the top ten customers	66.00%	67.00%
Profit or loss attributable to change in unrealized gains or losses for financial assets without quoted market prices held at end of period	$ 128	$ (1,329)	$ (74)
Profit or loss attributable to change in unrealized gains or losses for financial liabilities without quoted market prices held at end of period	119	(581)	829
Interest rate risk [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Increase (decrease) in profit due to percentage increase in market risk	45	36	19
Increase (decrease) in profit due to percentage decrease in market risk	$ (45)	$ (36)	$ (19)
Equity price risk [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Percentage increase in market risk	5.00%	5.00%	5.00%
Increase (decrease) in profit due to percentage increase in market risk	$ 261	$ 270	$ 285
Percentage decrease in market risk	5.00%	5.00%	5.00%
Increase (decrease) in profit due to percentage decrease in market risk	$ (261)	$ (270)	$ (285)
Increase (decrease) in other comprehensive income due to percentage increase in market risk	689	722	579
Increase (decrease) in other comprehensive income due to percentage decrease in market risk	$ (689)	$ (722)	$ (579)
Taiwan, New Dollars [member] | Currency risk [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Percentage increase in market risk	10.00%	10.00%	10.00%
Increase (decrease) in profit due to percentage increase in market risk	$ 1,095	$ 620	$ 1,305
Percentage decrease in market risk	10.00%	10.00%	10.00%
Increase (decrease) in profit due to percentage decrease in market risk	$ (1,095)	$ (620)	$ (1,305)
China, Yuan Renminbi [member] | Currency risk [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Percentage increase in market risk	10.00%	10.00%	10.00%
Increase (decrease) in profit due to percentage increase in market risk	$ 615	$ 582	$ 572
Percentage decrease in market risk	10.00%	10.00%	10.00%
Increase (decrease) in profit due to percentage decrease in market risk	$ (615)	$ (582)	$ (572)
Japan, Yen [member] | Currency risk [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Percentage increase in market risk	10.00%	10.00%	10.00%
Increase (decrease) in profit due to percentage increase in market risk	$ 237	$ 290	$ 538
Percentage decrease in market risk	10.00%	10.00%	10.00%
Increase (decrease) in profit due to percentage decrease in market risk	$ (237)	$ (290)	$ (538)
Financial assets at fair value through profit or loss, category [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Financial assets transfer from level two to level one		$ 655

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The gains (losses) recognised in profit or loss for assets measured at fair value that are attributable to the change in unrealised gains or losses relating to those assets held at the end of the reporting period. [Refer: At fair value [member]]

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