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Contents of Significant Accounts - Share-Based Payment - Additional Information (Detail) Right in Millions, $ in Millions |  |  |  |  |  |  | 1 Months Ended | 9 Months Ended | 12 Months Ended
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Dec. 05, 2024 | Dec. 05, 2023 | Dec. 05, 2022 | Jun. 09, 2021 | Sep. 30, 2020 | Sep. 01, 2020 | Jun. 30, 2021 Right | Sep. 30, 2020 Right | Dec. 31, 2024 TWD ($) | Dec. 31, 2023 TWD ($) | Dec. 31, 2022 TWD ($)
Restricted Stock Plan For Employees [Member] |  |  |  |  |  |  |  |  |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |  |  |  |  |  |  |  |  |
Compensation expenses | $ |  |  |  |  |  |  |  |  | $ 775 | $ 1,025 | $ 1,352
Eligibility terms to vested restricted stocks |  |  |  |  |  |  |  |  | Beginning from the end of two years since the date of grant, those employees who fulfill both service period and performance conditions set by UMC are gradually eligible to the vested restricted stocks at certain percentage and time frame. |  |
Life of plan | 4 years | 4 years | 4 years | 4 years |  | 4 years |  |  |  |  |
Stock Appreciation Right Plan For Employees [Member] |  |  |  |  |  |  |  |  |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |  |  |  |  |  |  |  |  |
Compensation expenses | $ |  |  |  |  |  |  |  |  | $ 20 | 105 | $ 210
Stock Appreciation Right Plan For Employees Description |  |  |  |  |  |  |  |  | One unit of stock appreciation right to employees represents a right to the intrinsic value of one common share of UMC. |  |
Life of plan |  |  |  |  | 4 years |  | 4 years |  |  |  |
Liabilities for stock appreciation right recognized |  |  |  |  |  |  |  |  | $ 8 | 207 |
Unit of cash-settled stock appreciation right | Right |  |  |  |  |  |  | 1 | 26 |  |  |
Intrinsic Value for the Liabilities of Vested Rights |  |  |  |  |  |  |  |  | $ 0 | $ 0 |

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- Definition The description of the vesting requirements for a type of share-based payment arrangement that existed at any time during the period. An entity with substantially similar types of share-based payment arrangements may aggregate this information. [Refer: Types of share-based payment arrangements [domain]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 2 -IssueDate 2024-01-01 -Paragraph 45 -Subparagraph a -URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2024-en-r&anchor=para_45_a&doctype=Standard -URIDate 2024-03-27 + Details
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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table. + References No definition available. + Details
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- Definition The amount of expense from share-based payment transactions with employees. [Refer: Expense from share-based payment transactions] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2024-01-01 -Paragraph 112 -Subparagraph c -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2024-en-r&anchor=para_112_c&doctype=Standard -URIDate 2024-03-27 + Details
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- Definition The intrinsic value of liabilities arising from share-based transactions for which the counterparty's right to cash or other assets had vested by the end of the period (for example, vested share appreciation rights). The intrinsic value is the difference between the fair value of the shares to which the counterparty has the (conditional or unconditional) right to subscribe, or which it has the right to receive, and the price (if any) that the counterparty is (or will be) required to pay for those shares. Share-based payment transactions are transactions in which the entity: (a) receives goods or services from the supplier of those goods or services (including an employee) in a share-based payment arrangement; or (b) incurs an obligation to settle the transaction with the supplier in a share-based payment arrangement when another group entity receives those goods or services, for which the counterparty's right to cash or other assets had vested by the end of the period (for example, vested share appreciation rights). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 2 -IssueDate 2024-01-01 -Paragraph 51 -Subparagraph b -Clause ii -URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2024-en-r&anchor=para_51_b_ii&doctype=Standard -URIDate 2024-03-27 + Details
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- Definition The amount of liabilities arising from share-based payment transactions. Share-based payment transactions are transactions in which the entity: (a) receives goods or services from the supplier of those goods or services (including an employee) in a share-based payment arrangement; or (b) incurs an obligation to settle the transaction with the supplier in a share-based payment arrangement when another group entity receives those goods or services. [Refer: Types of share-based payment arrangements [domain]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 2 -IssueDate 2024-01-01 -Paragraph 51 -Subparagraph b -Clause i -URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2024-en-r&anchor=para_51_b_i&doctype=Standard -URIDate 2024-03-27 + Details
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