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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 |  |
--- | --- | --- | ---
Dec. 31, 2019 TWD ($) | Dec. 31, 2018 TWD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2019 EUR (€) | Dec. 31, 2018 USD ($) | Dec. 31, 2018 EUR (€)
EUR [Member] |  |  |  |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |  |  |  |
Currency | EUR/NT$ | EUR/NT$ |  |  |  |
Maturity Period | 2020.03 | 2019.03-06 |  |  |  |
Contract Amount | $ 51 | $ 193 |  | € 2 |  | € 5
USD [Member] |  |  |  |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |  |  |  |
Currency | US$/NT$ | US$/NT$ |  |  |  |
Maturity Period | 2020.01 | 2019.01 |  |  |  |
Contract Amount | $ 26 | $ 62 | $ 1 |  | $ 2 |

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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 2019-01-01 -Paragraph 112 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_112_c&doctype=Standard -URIDate 2019-03-27 + Details
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