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Earnings Per Share - Net Income and Weighted Average Number of Common Stocks Used in Calculation of Earnings Per Share (Detail) shares in Millions, $ in Millions, $ in Millions | 12 Months Ended
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Dec. 31, 2018 TWD ($) shares | Dec. 31, 2018 USD ($) shares | Dec. 31, 2017 TWD ($) shares | Dec. 31, 2016 TWD ($) shares
Net income used to compute the basic earnings per share |  |  |  |
Net income attributable to the parent | $ 37,557 | $ 1,227 | $ 38,988 | $ 40,485
Assumed conversion of all dilutive potential common stocks |  |  |  |
Employee stock options, employee compensation of subsidiaries | $ | (6) |  | 0 | (1)
Net income used to compute the diluted earnings per share | $ | $ 37,551 |  | $ 38,988 | $ 40,484
Weighted average number of common stocks used to compute the basic earnings per share | 7,757 | 7,757 | 7,757 | 7,757
Assumed conversion of all dilutive potential common stocks |  |  |  |
Employee compensation | 9 | 9 | 11 | 12
Weighted average number of common stocks used to compute the diluted earnings per share | 7,766 | 7,766 | 7,768 | 7,769

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- Definition The weighted average number of ordinary shares outstanding plus the weighted average number of ordinary shares that would be issued on the conversion of all the dilutive potential ordinary shares into ordinary shares. [Refer: Ordinary shares [member]; Weighted average [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 33 -IssueDate 2018-01-01 -Paragraph 70 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=33&date=2018-03-01&anchor=para_70_b&doctype=Standard -URIDate 2018-03-16 + Details
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- Definition The number of dilutive potential ordinary shares that relate to the assumed exercise of the entity's share options. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 33 -IssueDate 2018-01-01 -Paragraph 70 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=33&date=2018-03-01&anchor=para_70_b&doctype=Standard -URIDate 2018-03-16 + Details
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- Definition The profit (loss) attributable to ordinary equity holders of the parent equity, adjusted for the effects of all dilutive potential ordinary shares. [Refer: Profit (loss)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 33 -IssueDate 2018-01-01 -Paragraph 70 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=33&date=2018-03-01&anchor=para_70_a&doctype=Standard -URIDate 2018-03-16 + Details
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- Definition The profit (loss) from continuing and discontinued operations attributable to owners of the parent. [Refer: Profit (loss)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2018-01-01 -Paragraph 81B -Subparagraph a -Clause ii -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_81B_a_ii&doctype=Standard -URIDate 2018-03-16 + Details
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- Definition The number of ordinary shares outstanding at the beginning of the period, adjusted by the number of ordinary shares bought back or issued during the period multiplied by a time-weighting factor. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 33 -IssueDate 2018-01-01 -Paragraph 70 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=33&date=2018-03-01&anchor=para_70_b&doctype=Standard -URIDate 2018-03-16 + Details
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