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Income Tax Expense - Details of Deferred Tax Assets (Liabilities) (Detail) $ in Thousands, $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 TWD ($) | Dec. 31, 2018 TWD ($) | Dec. 31, 2017 TWD ($) | Dec. 31, 2019 USD ($)
Disclosure of the detail of deferred tax assets and liabilities [line items] |  |  |  |
Recognized in profit or loss | $ (35,367) | $ (98,667) | $ (110,542) |
Deferred tax assets | 194,552 | 226,716 | 212,372 | $ 6,505
Deferred tax liabilities | (309,129) | (308,759) | (174,293) | $ (10,335)
Deferred tax assets unrealized loss on inventories [member] |  |  |  |
Disclosure of the detail of deferred tax assets and liabilities [line items] |  |  |  |
Beginning balance | 7,232 | 9,132 |  |
Effects on initial application of IFRS 9 and IFRS 15 |  | (770) |  |
Recognized in profit or loss | 5,468 | (1,130) |  |
Ending balance | 12,700 | 7,232 | 9,132 |
Property, plant and equipment, deferred tax assets [member] |  |  |  |
Disclosure of the detail of deferred tax assets and liabilities [line items] |  |  |  |
Beginning balance | 64,183 | 55,494 |  |
Recognized in profit or loss | (25,515) | 8,689 |  |
Ending balance | 38,668 | 64,183 | 55,494 |
Provisions [member] |  |  |  |
Disclosure of the detail of deferred tax assets and liabilities [line items] |  |  |  |
Beginning balance | 12,396 | 21,643 |  |
Recognized in profit or loss | (6,796) | (9,247) |  |
Ending balance | 5,600 | 12,396 | 21,643 |
Deferred tax assets deferred revenue [member] |  |  |  |
Disclosure of the detail of deferred tax assets and liabilities [line items] |  |  |  |
Beginning balance | 34,156 | 39,485 |  |
Recognized in profit or loss | (6,506) | (5,329) |  |
Ending balance | 27,650 | 34,156 | 39,485 |
Net defined benefit liability [member] |  |  |  |
Disclosure of the detail of deferred tax assets and liabilities [line items] |  |  |  |
Beginning balance | 100,743 | 78,451 |  |
Recognized in profit or loss | (3,948) | 7,889 |  |
Recognized in other comprehensive income | (4,183) | 14,403 |  |
Ending balance | 92,612 | 100,743 | 78,451 |
Unrealized exchange losses deferred tax assets [member] |  |  |  |
Disclosure of the detail of deferred tax assets and liabilities [line items] |  |  |  |
Beginning balance | 3,575 | 8,167 |  |
Effects on initial application of IFRS 9 and IFRS 15 |  | 144 |  |
Recognized in profit or loss | 13,721 | (4,736) |  |
Ending balance | 17,296 | 3,575 | 8,167 |
Investment tax credit [member] |  |  |  |
Disclosure of the detail of deferred tax assets and liabilities [line items] |  |  |  |
Beginning balance | 4,420 |  |  |
Recognized in profit or loss | (4,420) | 4,420 |  |
Ending balance |  | 4,420 |  |
Other [member] |  |  |  |
Disclosure of the detail of deferred tax assets and liabilities [line items] |  |  |  |
Beginning balance | 11 |  |  |
Recognized in profit or loss | 15 | 11 |  |
Ending balance | 26 | 11 |  |
Deferred tax asset [member] |  |  |  |
Disclosure of the detail of deferred tax assets and liabilities [line items] |  |  |  |
Beginning balance | 226,716 | 212,372 |  |
Effects on initial application of IFRS 9 and IFRS 15 |  | (626) |  |
Recognized in profit or loss | (27,981) | 567 |  |
Recognized in other comprehensive income | (4,183) | 14,403 |  |
Ending balance | 194,552 | 226,716 | 212,372 |
Property, plant and equipment, deferred tax liabilities [member] |  |  |  |
Disclosure of the detail of deferred tax assets and liabilities [line items] |  |  |  |
Beginning balance | (281,594) | (174,293) |  |
Recognized in profit or loss | (7,386) | (107,301) |  |
Ending balance | (288,980) | (281,594) | (174,293) |
Deferred tax liabilities, contract assets [member] |  |  |  |
Disclosure of the detail of deferred tax assets and liabilities [line items] |  |  |  |
Effects on initial application of IFRS 9 and IFRS 15 |  | (8,067) |  |
Recognized in profit or loss |  | 8,067 |  |
Financial assets at fair value through other comprehensive income [member] |  |  |  |
Disclosure of the detail of deferred tax assets and liabilities [line items] |  |  |  |
Beginning balance | (27,165) |  |  |
Effects on initial application of IFRS 9 and IFRS 15 |  | (8,636) |  |
Recognized in other comprehensive income | 7,016 | (18,529) |  |
Ending balance | (20,149) | (27,165) |  |
Deferred tax liabilities [member] |  |  |  |
Disclosure of the detail of deferred tax assets and liabilities [line items] |  |  |  |
Beginning balance | (308,759) | (174,293) |  |
Effects on initial application of IFRS 9 and IFRS 15 |  | (16,703) |  |
Recognized in profit or loss | (7,386) | (99,234) |  |
Recognized in other comprehensive income | 7,016 | (18,529) |  |
Ending balance | $ (309,129) | $ (308,759) | $ (174,293) |

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