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Capital stock - Additional Information (Detail) $ / shares in Units, $ in Thousands, $ in Thousands |  |  | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Aug. 06, 2019 TWD ($) shares | Mar. 07, 2019 TWD ($) shares | Dec. 31, 2021 TWD ($) $ / shares shares | Dec. 31, 2021 USD ($) shares | Dec. 31, 2020 TWD ($)
Disclosure of classes of share capital [line items] |  |  |  |  |
Ordinary shares par value | $ / shares |  |  | $ 10 |  |
Number of shares outstanding |  |  | 727,240,000 | 727,240,000 |
Authorised capital | $ |  |  | $ 9,700,000 |  |
Number of shares authorized |  |  | 970,000,000 | 970,000,000 |
Paid in capital |  |  | $ 7,272,401 | $ 262,163 | $ 7,272,401
Approval for number of treasury stock cancelled | 25,570,000 | 25,570,000 |  |  |
Cancellation of treasury stock | $ | $ 962,503 | $ 962,503 |  |  |
Ordinary shares [member] |  |  |  |  |
Disclosure of classes of share capital [line items] |  |  |  |  |
Number of shares outstanding |  |  | 91,725,000 | 91,725,000 |
American depositary shares [member] |  |  |  |  |
Disclosure of classes of share capital [line items] |  |  |  |  |
Number of shares represented by each unit of ADS |  |  | 20 |  |
Number of shares outstanding |  |  | 4,586,252 | 4,586,252 |

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