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Borrowings - Summary of Long-term Bills Payable (Detail) $ in Thousands, $ in Thousands | Dec. 31, 2017 TWD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 TWD ($)
--- | --- | --- | ---
Disclosure of detailed information about borrowings [line items] |  |  |
Long-term bills payable | $ 1,999,132 | $ 67,447 | $ 1,999,341
Unamortized Discounts [member] |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |
Long-term bills payable | 868 | 29 | 659
Longterm Bills Payable [member] |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |
Long-term bills payable | 2,000,000 | 67,476 | 2,000,000
China Bills Finance Corporation [member] |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |
Long-term bills payable | 1,000,000 | 33,738 |
International Bills Finance Corporation [member] |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |
Long-term bills payable | $ 1,000,000 | $ 33,738 |
Ta Ching Bills Finance Corporation [member] |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |
Long-term bills payable |  |  | $ 2,000,000

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