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Earnings Per Share - Summary of Earnings and Weighted Average Number of Ordinary Shares Outstanding in Computation of Earnings Per Share (Detail) shares in Thousands, $ in Thousands, $ in Thousands | 12 Months Ended
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Dec. 31, 2019 TWD ($) shares | Dec. 31, 2019 USD ($) shares | Dec. 31, 2018 TWD ($) shares | Dec. 31, 2017 TWD ($) shares
Earnings per share [line items] |  |  |  |
Profit for the year attributable to owners of the Company | $ 17,060,591 | $ 570,397 | $ 26,220,721 | $ 22,819,119
Effect of potentially dilutive ordinary shares: |  |  |  |
From subsidiaries' potentially dilutive ordinary shares | (385,865) | (12,901) | (418,295) | (813,627)
From the investments in associates | $ |  |  |  | (367,687)
From convertible bonds | $ |  |  |  | 93,781
Earnings used in the computation of diluted earnings per share | $ 16,674,726 | $ 557,496 | $ 25,802,426 | $ 21,731,586
Weighted average number of ordinary shares in the computation of basic earnings per share | 4,251,964 | 4,251,964 | 4,245,247 | 4,080,443
Effect of potentially dilutive ordinary shares: |  |  |  |
From convertible bonds |  |  |  | 62,456
From employee share options | 10,232 | 10,232 | 5,103 | 19,934
From employees' compensation | 570 | 570 | 779 | 21,787
Weighted average number of ordinary shares in computation of diluted earnings per share | 4,262,766 | 4,262,766 | 4,251,129 | 4,184,620

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