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Available-for-sale Financial Assets Non Current - Additional Information (Detail) $ in Millions | 12 Months Ended
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Dec. 31, 2018 TWD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 TWD ($) | Dec. 31, 2016 TWD ($)
Disclosure Of Financial Assets [Line Items] |  |  |  |
Impairment loss on available-for-sale financial assets | $ 0 | $ 0 | $ 0 | $ 577,000,000
Amount invested in investment entity |  |  | 5,751,000,000 |
Carrying value of non-listed available-for-sale financial assets disposed |  |  | 5,000,000 | 9,000,000
Gains (losses) from disposal of available-for-sale assets |  |  | 3,000,000 | 1,000,000
Taiwania Capital Buffalo Fund Co Ltd [Member] |  |  |  |
Disclosure Of Financial Assets [Line Items] |  |  |  |
Amount invested in investment entity |  |  | $ 300,000,000 |
Ownership percentage in investment entity |  |  | 12.90% |
Domestic listed stocks [Member] |  |  |  |
Disclosure Of Financial Assets [Line Items] |  |  |  |
Impairment loss on available-for-sale financial assets |  |  | $ 0 | 577,000,000
Amount invested in investment entity |  |  | 3,125,000,000 |
Non-listed stocks [Member] |  |  |  |
Disclosure Of Financial Assets [Line Items] |  |  |  |
Impairment loss on available-for-sale financial assets |  |  | $ 0 | $ 0

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- Definition Impairment loss (reversal of impairment loss) recognised in profit or loss available-for-sale financial assets. + References No definition available. + Details
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- Definition The amount of non-derivative financial assets that are designated as available for sale or are not classified as (a) loans and receivables; (b) held-to-maturity investments; or (c) financial assets at fair value through profit or loss. [Refer: Derivative financial assets; Financial assets at fair value through profit or loss; Held-to-maturity investments] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Note Expiry date 2021-01-01 -Name IFRS -Number 7 -IssueDate 2018-01-01 -Paragraph 8 -Subparagraph d -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-02&anchor=para_8_d&doctype=Standard&book=b -URIDate 2018-03-16 + Details
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- Definition The gains (losses) on available-for-sale financial assets. [Refer: Financial assets available-for-sale] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Note Expiry date 2021-01-01 -Name IFRS -Number 7 -IssueDate 2018-01-01 -Paragraph 20 -Subparagraph a -Clause ii -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-02&anchor=para_20_a_ii&doctype=Standard&book=b -URIDate 2018-03-16 + Details
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