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Earnings Per Share - Income and Share Data Used in Basic and Diluted EPS Computations (Detail) $ / shares in Units, shares in Thousands, $ in Thousands | 12 Months Ended
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Dec. 31, 2020 TWD ($) $ / shares shares | Dec. 31, 2020 $ / shares | Dec. 31, 2019 TWD ($) $ / shares shares | Dec. 31, 2018 TWD ($) $ / shares shares
Basic earnings per share, amount after tax |  |  |  |
Equity holders of the Company - Amount after tax | $ | $ 2,378,978 |  | $ 2,508,574 | $ 1,325,824
Diluted earnings per share, amount after tax |  |  |  |
Equity holders of the Company - Amount after tax | $ | $ 2,378,978 |  | $ 2,508,574 | $ 1,325,824
Weighted average number of ordinary shares outstanding | 727,240 |  | 727,111 | 802,725
Diluted earnings per share, weighted-average number of ordinary shares outstanding |  |  |  |
Employees' compensations | 9,668 |  | 9,879 | 7,626
Restricted shares |  |  | 126 | 3,356
Weighted average number of ordinary shares outstanding | 736,908 |  | 737,116 | 813,707
Ordinary shares [member] |  |  |  |
Basic earnings per share |  |  |  |
Equity holders of the Company - Earnings per share | (per share) | $ 3.27 | $ 0.12 | $ 3.45 | $ 1.65
Diluted earnings per share |  |  |  |
Equity holders of the Company - Earnings per share | (per share) | $ 3.23 | $ 0.11 | $ 3.40 | $ 1.63

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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 2020-01-01 -Paragraph 70 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=33&code=ifrs-tx-2020-en-r&anchor=para_70_b&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator) divided by the weighted average number of ordinary shares outstanding during the period (the denominator). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 33 -IssueDate 2020-01-01 -Paragraph 66 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=33&code=ifrs-tx-2020-en-r&anchor=para_66&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator), divided by the weighted average number of ordinary shares outstanding during the period (the denominator), both adjusted for the effects of all dilutive potential ordinary shares. [Refer: Ordinary shares [member]; Weighted average [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 33 -IssueDate 2020-01-01 -Paragraph 66 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=33&code=ifrs-tx-2020-en-r&anchor=para_66&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The profit (loss) attributable to ordinary equity holders of the parent entity. [Refer: Profit (loss)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 33 -IssueDate 2020-01-01 -Paragraph 70 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=33&code=ifrs-tx-2020-en-r&anchor=para_70_a&doctype=Standard -URIDate 2020-01-01 + Details
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