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Contents of Significant Accounts - Significant Components of Deferred Income Tax Assets and Liabilities (Detail) $ in Thousands, $ in Thousands | Dec. 31, 2024 TWD ($) | Dec. 31, 2024 USD ($) | Dec. 31, 2023 TWD ($) | Dec. 31, 2022 TWD ($)
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Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | $ 5,224,503 | $ 159,332 | $ 5,130,411 |
Deferred income tax liabilities | (8,118,251) | $ (247,583) | (5,631,964) |
Net deferred income tax assets (liabilities) | (2,893,748) |  | (501,553) | $ 1,663,800
Depreciation [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | 2,616,538 |  | 2,396,554 |
Deferred income tax liabilities | (4,387,572) |  | (2,085,916) |
Pension [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | 281,385 |  | 436,129 |
Refund liabilities [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | 318,156 |  | 306,408 |
Allowance for inventory valuation losses [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | 726,023 |  | 682,909 |
Investment loss [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | 328,241 |  | 314,427 |
Unrealized profit on intercompany sales [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | 471,583 |  | 689,124 |
Others [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | 482,577 |  | 304,860 |
Deferred income tax liabilities | (354,201) |  | (374,109) |
Investment gain [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax liabilities | (3,093,367) |  | (2,888,534) |
Amortizable assets [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax liabilities | $ (283,111) |  | $ (283,405) |

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- Definition The amounts of income taxes recoverable in future periods in respect of: (a) deductible temporary differences; (b) the carryforward of unused tax losses; and (c) the carryforward of unused tax credits. [Refer: Temporary differences [member]; Unused tax credits [member]; Unused tax losses [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2024-01-01 -Paragraph 81 -Subparagraph g -Clause i -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2024-en-r&anchor=para_81_g_i&doctype=Standard -URIDate 2024-03-27 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2024-01-01 -Paragraph 54 -Subparagraph o -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2024-en-r&anchor=para_54_o&doctype=Standard -URIDate 2024-03-27 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2024-01-01 -Paragraph 56 -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2024-en-r&anchor=para_56&doctype=Standard -URIDate 2024-03-27 + Details
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