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Long-term Bank Loans - Summary of Long-term Bank Loans (Detail) $ in Thousands, $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 TWD ($) | Dec. 31, 2019 TWD ($) | Dec. 31, 2020 USD ($)
Disclosure of detailed information about borrowings [Line Items] |  |  |
Bank loans | $ 7,733,565 | $ 9,041,645 |
Less:Fee on syndicated bank loan | (17,223) | (24,355) |
Less: Unamortized interest on government granted bank loans | (64,212) |  |
Less: Current portion (fee included) | (748,353) | (748,419) | $ (26,651)
Syndicated bank loans, excluding current portion | 6,985,212 | 8,293,226 | $ 248,761
Long-term bank loans [Member] |  |  |
Disclosure of detailed information about borrowings [Line Items] |  |  |
Unused credit lines of long-term | $ 11,239,000 | $ 1,800,000 |
Gross carrying amount [member] |  |  |
Disclosure of detailed information about borrowings [Line Items] |  |  |
Interest rate range |  | 1.7895% |
Gross carrying amount [member] | Minimum [Member] |  |  |
Disclosure of detailed information about borrowings [Line Items] |  |  |
Interest rate range | 0.65% |  | 0.65%
Gross carrying amount [member] | Maximum [Member] |  |  |
Disclosure of detailed information about borrowings [Line Items] |  |  |
Interest rate range | 1.7895% |  | 1.7895%
Gross carrying amount [member] | Syndicated bank loans repayable from November 2018 to May 2023 [member] |  |  |
Disclosure of detailed information about borrowings [Line Items] |  |  |
Bank loans | $ 3,310,000 | $ 9,066,000 |
Period and payment term | Borrowing period is from May 30, 2018 to May 30, 2023; interest is repayable monthly; principal is repayable semi-annually from November 30, 2018 | Borrowing period is from May 30, 2018 to May 30, 2023; interest is repayable monthly; principal is repayable semi-annually from November 30, 2018 |
Gross carrying amount [member] | Government granted bank loans from March 2020 To February 2030 [Member] |  |  |
Disclosure of detailed information about borrowings [Line Items] |  |  |
Bank loans | $ 4,505,000 |  |
Period and payment term | Borrowing period is from March 11, 2020 to February 15, 2030; interest is repayable monthly; principal is repayable monthly from March 15, 2023 |  |

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