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Significant Contingent Liabilities and Unrecognized Commitments - Additional Information (Detail) $ in Thousands, $ in Thousands | 1 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Dec. 31, 2013 TWD ($) | Dec. 31, 2019 TWD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 TWD ($) | Jan. 31, 2020 TWD ($) | Jan. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Feb. 28, 2019 TWD ($) | Feb. 28, 2019 USD ($) | Dec. 31, 2013 USD ($)
Disclosure of contingent liabilities [line items] |  |  |  |  |  |  |  |  |  |
Unused letters of credit |  | $ 394,000 |  | $ 634,000 |  |  | $ 13,173 |  |  |
Committed to purchase property, plant and equipment |  | 25,119,371 |  | 17,039,458 |  |  | 839,832 |  |  |
Prepayment of property, plant and equipment |  | 5,145,345 | $ 172,028 | 2,339,308 |  |  |  |  |  |
Construction contract related to real estate business |  | 1,393,859 | $ 46,602 | $ 888,052 |  |  |  |  |  |
Contractual period for environmental protection | 30 years |  |  |  |  |  |  |  |  |
Letter of credits |  | $ 952,001 |  |  |  |  | $ 31,829 |  |  |
Taiwan [member] |  |  |  |  |  |  |  |  |  |
Disclosure of contingent liabilities [line items] |  |  |  |  |  |  |  |  |  |
Contribution to be made for environmental protection | $ 3,000,000 |  |  |  |  |  |  | $ 100,000 | $ 3,343 | $ 100,301
Taiwan [member] | Announcing or commencing implementation of major restructuring [member] |  |  |  |  |  |  |  |  |  |
Disclosure of contingent liabilities [line items] |  |  |  |  |  |  |  |  |  |
Contribution to be made for environmental protection |  |  |  |  | $ 100,000 | $ 3,343 |  |  |  |

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