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Equity - Additional Information (Detail) $ / shares in Units, $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 TWD ($) shares | Dec. 31, 2018 TWD ($) $ / shares shares
Disclosure of classes of share capital [line items] |  |
Number of shares represented by each ADS | 2 |
Percentage of legal reserve on share capital |  | 25.00%
Cash dividends paid from the capital surplus | $ | $ 10,795,980 | $ (10,795,980)
American depository shares (ADs) [member] |  |
Disclosure of classes of share capital [line items] |  |
Number of shares represented by each ADS | 2 |
Number of shares outstanding | 125,542,000 | 140,042,000
Ordinary shares [member] |  |
Disclosure of classes of share capital [line items] |  |
Number of shares outstanding | 251,084,000 | 280,085,000
A.S.E. Holding Limited [member] |  |
Disclosure of classes of share capital [line items] |  |
Repurchase of ordinary shares |  | 1,852,000
Repurchase of ordinary shares, price per share | $ / shares |  | $ 38.5
Treasury shares canceled |  | 121,852,000
Top of range [member] |  |
Disclosure of classes of share capital [line items] |  |
Percentage of cash dividend on dividend distribution |  | 30.00%

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- Definition The number of shares that have been authorised and issued, reduced by treasury shares held. [Refer: Treasury shares] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2019-01-01 -Paragraph 79 -Subparagraph a -Clause iv -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_79_a_iv&doctype=Standard -URIDate 2019-03-27 + Details
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