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Financial Instruments at Fair Value Through Profit or Loss - Outstanding Forward Exchange Contracts Not Designated for Hedge (Detail) - Forward exchange contracts [Member] € in Millions, $ in Millions, $ in Millions | 12 Months Ended |  |
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Dec. 31, 2020 TWD ($) | Dec. 31, 2019 TWD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2020 EUR (€) | Dec. 31, 2019 USD ($) | Dec. 31, 2019 EUR (€)
EUR [Member] |  |  |  |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |  |  |  |
Currency | NT$/EUR | NT$/EUR |  |  |  |
Maturity Period | 2021.03 | 2020.03 |  |  |  |
Contract Amount | $ 50 | $ 51 |  | € 2 |  | € 2
USD [Member] |  |  |  |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |  |  |  |
Currency |  | NT$/US$ |  |  |  |
Maturity Period |  | 2020.01 |  |  |  |
Contract Amount |  | $ 26 |  |  | $ 1 |
Taiwan, New Dollars |  |  |  |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |  |  |  |
Currency | US$/NT$ |  |  |  |  |
Maturity Period | 2021.02-03 |  |  |  |  |
Contract Amount | $ 379 |  | $ 14 |  |  |

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- Definition Derivative contract, cross currency. + References No definition available. + Details
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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
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- Definition The nominal or face amount of a financial instrument, used to calculate payments made on that instrument. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 112 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_112_c&doctype=Standard -URIDate 2020-01-01 + Details
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- Details
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