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Profit Before Income Tax - Additional Information (Detail) $ in Thousands, $ in Thousands | 1 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2016 | Dec. 31, 2017 TWD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 TWD ($) | Dec. 31, 2015
Analysis of income and expense [Line Items] |  |  |  |  |
Percentage of employees' compensation |  | 8.25% | 8.25% | 8.25% | 8.25%
Percentage of remuneration to directors |  | 0.75% | 0.75% | 0.75% | 0.75%
Difference between paid and recognized value of employees' compensation and remuneration to directors |  | $ 42,634 | $ 1,438 | $ 44,200 |
Bottom of range [member] |  |  |  |  |
Analysis of income and expense [Line Items] |  |  |  |  |
Percentage of employees' compensation | 5.25% |  |  |  |
Top of range [member] |  |  |  |  |
Analysis of income and expense [Line Items] |  |  |  |  |
Percentage of employees' compensation | 8.25% |  |  |  |

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