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Borrowings - Summary of Bills Payable (Detail) $ in Thousands, $ in Thousands | Dec. 31, 2019 TWD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 TWD ($)
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Disclosure of detailed information about borrowings [line items] |  |  |
Long-term bills payable | $ 10,895,365 | $ 364,272 | $ 3,099,232
Unamortized Discounts [member] |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |
Long-term bills payable | 4,635 | 155 | 768
Longterm Bills Payable [member] |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |
Long-term bills payable | 10,900,000 | 364,427 | 3,100,000
China Bills Finance Corporation [member] |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |
Long-term bills payable | 2,800,000 | 93,614 | 1,000,000
International Bills Finance Corporation [member] |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |
Long-term bills payable | 3,000,000 | 100,301 | 1,000,000
Ta Ching Bills Finance Corporation [member] |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |
Long-term bills payable | 3,100,000 | 103,644 | $ 1,100,000
Mega Bills Finance Corporation [Member] |  |  |
Disclosure of detailed information about borrowings [line items] |  |  |
Long-term bills payable | $ 2,000,000 | $ 66,868 |

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- Details
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