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Financial Assets at Fair Value through Other Comprehensive Income Noncurrent - Additional Information (Detail) - TWD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Noncurrent Financial Assets At Fair Value Through Other Comprehensive Income [Abstract] |  |  |
fair value amount | $ 568 |  |
Investment settlement fuds | 270 |  |
Unrealized gain on investments in equity instruments at fair value through other comprehensive income | 17 |  |
Dividends received | $ 246 | $ 296 | $ 396

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- Definition The amount of other comprehensive income, net of tax, related to gains (losses) from changes in the fair value of investments in equity instruments that the entity has designated at fair value through other comprehensive income. [Refer: Other comprehensive income] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 7 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_7&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 91 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_91_a&doctype=Standard -URIDate 2020-01-01 + Details
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