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Contents of Significant Accounts - Significant Components of Deferred Income Tax Assets and Liabilities (Detail) $ in Thousands, $ in Thousands | Dec. 31, 2023 TWD ($) | Dec. 31, 2023 USD ($) | Dec. 31, 2022 TWD ($) | Dec. 31, 2021 TWD ($)
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Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | $ 5,130,411 | $ 167,551 | $ 5,226,236 |
Deferred income tax liabilities | (5,631,964) | $ (183,931) | (3,562,436) |
Net deferred income tax assets (liabilities) | (501,553) |  | 1,663,800 | $ 3,154,352
Depreciation [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | 2,396,554 |  | 2,056,568 |
Deferred income tax liabilities | (2,085,916) |  | (70,133) |
Pension [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | 436,129 |  | 569,193 |
Refund liabilities [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | 306,408 |  | 138,617 |
Allowance for inventory valuation losses [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | 682,909 |  | 507,621 |
Investment loss [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | 314,427 |  | 474,405 |
Unrealized profit on intercompany sales [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | 689,124 |  | 906,793 |
Others [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax assets | 304,860 |  | 573,039 |
Deferred income tax liabilities | (374,109) |  | (544,863) |
Investment gain [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax liabilities | (2,888,534) |  | (2,648,989) |
Amortizable assets [member] |  |  |  |
Disclosure Of Deferred Taxes [Line Items] |  |  |  |
Deferred income tax liabilities | $ (283,405) |  | $ (298,451) |

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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 2023-01-01 -Paragraph 81 -Subparagraph g -Clause i -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2023-en-r&anchor=para_81_g_i&doctype=Standard -URIDate 2023-03-23 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2023-01-01 -Paragraph 54 -Subparagraph o -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2023-en-r&anchor=para_54_o&doctype=Standard -URIDate 2023-03-23 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2023-01-01 -Paragraph 56 -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2023-en-r&anchor=para_56&doctype=Standard -URIDate 2023-03-23 + Details
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