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Contents of Significant Accounts - Reconciliation Between Income Tax Expense and Income Before Tax At UMC's Applicable Tax Rate (Detail) $ in Thousands, $ in Thousands | 12 Months Ended
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Dec. 31, 2023 TWD ($) | Dec. 31, 2023 USD ($) | Dec. 31, 2022 TWD ($) | Dec. 31, 2021 TWD ($)
Reconciliation of accounting profit multiplied by applicable tax rates [abstract] |  |  |  |
Income before tax | $ 68,450,404 | $ 2,235,480 | $ 109,625,660 | $ 58,496,432
At UMC's statutory income tax rate | 13,690,081 |  | 21,925,132 | 11,699,286
Adjustments in respect of current income tax of prior periods | (217,891) |  | (585,941) | (150,260)
Net changes in loss carry-forward and investment tax credits | (2,179,234) |  | (465,152) | (845,267)
Adjustment of deferred tax assets/liabilities for write-downs/reversals and different jurisdictional tax rates | 211,639 |  | (281,319) | 183,123
Tax effect of non-taxable income and non-deductible expenses: |  |  |  |
Tax exempt income | (1,428,035) |  | (4,384,566) | (3,258,695)
Investment loss (gain) | (755,800) |  | 1,827,822 | (1,388,877)
Dividend income | (323,182) |  | (423,027) | (171,725)
Others | (145,520) |  | (340,745) | 6,463
Basic tax | 43,506 |  | 0 | 0
Estimated income tax on unappropriated earnings | (1,160,324) |  | 1,247,910 | 1,558,031
Effect of different tax rates applicable to UMC and its subsidiaries | 234,510 |  | 605,929 | 116,174
Taxes withheld in other jurisdictions | 38,346 |  | 35,979 | 43,443
Others | 303,174 |  | 164,873 | 126,556
Income tax expense recorded in profit or loss | $ 8,311,270 | $ 271,433 | $ 19,326,895 | $ 7,918,252

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- Definition The aggregate amount included in the determination of profit (loss) for the period in respect of current tax and deferred tax. [Refer: Current tax expense (income); Deferred tax expense (income)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 8 -IssueDate 2023-01-01 -Paragraph 23 -Subparagraph h -URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2023-en-r&anchor=para_23_h&doctype=Standard -URIDate 2023-03-23 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 26 -IssueDate 2023-01-01 -Paragraph 35 -Subparagraph b -Clause viii -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=26&code=ifrs-tx-2023-en-r&anchor=para_35_b_viii&doctype=Standard -URIDate 2023-03-23 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2023-01-01 -Paragraph 79 -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2023-en-r&anchor=para_79&doctype=Standard -URIDate 2023-03-23 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2023-01-01 -Paragraph 81 -Subparagraph c -Clause i -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2023-en-r&anchor=para_81_c_i&doctype=Standard -URIDate 2023-03-23 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2023-01-01 -Paragraph 81 -Subparagraph c -Clause ii -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2023-en-r&anchor=para_81_c_ii&doctype=Standard -URIDate 2023-03-23 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 12 -IssueDate 2023-01-01 -Paragraph B13 -Subparagraph g -URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2023-en-r&anchor=para_B13_g&doctype=Appendix&subtype=B -URIDate 2023-03-23 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2023-01-01 -Paragraph 82 -Subparagraph d -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2023-en-r&anchor=para_82_d&doctype=Standard -URIDate 2023-03-23 + Details
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- Definition The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that the entity does not separately disclose in the same statement or note. [Refer: Accounting profit; Applicable tax rate] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2023-01-01 -Paragraph 81 -Subparagraph c -Clause i -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2023-en-r&anchor=para_81_c_i&doctype=Standard -URIDate 2023-03-23 + Details
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- Definition The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that relates to foreign tax rates. [Refer: Accounting profit] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2023-01-01 -Paragraph 81 -Subparagraph c -Clause i -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2023-en-r&anchor=para_81_c_i&doctype=Standard -URIDate 2023-03-23 + Details
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