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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, 2018 TWD ($) | Dec. 31, 2017 TWD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2018 EUR (€) | Dec. 31, 2017 USD ($) | Dec. 31, 2017 EUR (€)
EUR [Member] |  |  |  |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |  |  |  |
Currency | EUR/NT$ | EUR/NT$ |  |  |  |
Maturity Period | 2019.03-06 | 2018.03-06 |  |  |  |
Contract Amount | $ 193 | $ 69 |  | € 5 |  | € 2
USD [Member] |  |  |  |  |  |
Disclosure of detailed information about financial instruments [Line Items] |  |  |  |  |  |
Currency | US$/NT$ | US$/NT$ |  |  |  |
Maturity Period | 2019.01 | 2018.01 |  |  |  |
Contract Amount | $ 62 | $ 125 | $ 2 |  | $ 4 |

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- Definition Derivative contract, cross currency. + References No definition available. + Details
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- Definition Description of derivative financial instruments maturity period. + 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 Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Details
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- Details
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- Details
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