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Financial Assets at Fair Value Through Other Comprehensive Income - Additional Information (Detail) Bonds in Thousands, $ in Thousands, $ in Thousands | 1 Months Ended |  |
--- | --- | --- | ---
Jun. 30, 2016 TWD ($) Bonds | Dec. 31, 2018 USD ($) | Dec. 31, 2018 TWD ($) | Dec. 31, 2017 TWD ($)
Financial assets at fair value through other comprehensive income [line items] |  |  |  |
Unsecured subordinate corporate bonds amount |  | $ 247,754 | $ 7,583,761 | $ 1,642,840
Unsecured subordinate corporate bonds [member] |  |  |  |
Financial assets at fair value through other comprehensive income [line items] |  |  |  |
Unsecured subordinate corporate bonds amount | $ | $ 1,000,000 |  |  | $ 1,000,000
Number of bonds acquired | Bonds | 1,000 |  |  |
Corporate bonds annual interest rate | 3.50% |  |  |
Effective interest rate |  | 3.20% | 3.20% | 3.20%

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