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Contents of Significant Accounts - Share-Based Payment - Additional Information (Detail) $ / shares in Units, shares in Millions, Right in Millions, $ in Millions |  |  |  |  |  |  |  |  | 1 Months Ended | 12 Months Ended
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Dec. 05, 2023 $ / shares shares | Dec. 05, 2022 $ / shares shares | May 27, 2022 shares | Jun. 30, 2021 | Jun. 09, 2021 $ / shares shares | Sep. 30, 2020 | Sep. 01, 2020 $ / shares shares | Jun. 10, 2020 shares | Jun. 30, 2021 Right | Sep. 30, 2020 Right | Dec. 31, 2023 TWD ($) | Dec. 31, 2022 TWD ($) | Dec. 31, 2021 TWD ($) | Dec. 31, 2020
Restricted Stock Plan For Employees [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Compensation expenses | $ |  |  |  |  |  |  |  |  |  |  | $ 1,025 | $ 1,352 | $ 1,520 |
Compensation plan description |  |  |  |  |  |  |  |  |  |  | UMC is authorized to issue restricted stocks in one tranche or in installments, under the custody of trust institution, within two years from the date of receiving the effective declaration from the competent authority. |  |  | UMC is authorized to issue restricted stocks in one tranche or in installments, under the custody of trust institution, within one year from the date of receiving the effective declaration from the competent authority.
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. |  |  |
Maximum shares to be issued under compensation plan | shares | shares |  |  | 50 |  |  |  |  | 233 |  |  |  |  |  |
Shares of restricted stock for employees issued | shares | shares | 27 | 23 |  |  | 1 |  | 200 |  |  |  |  |  |  |
Life of plan | 4 years | 4 years |  |  | 4 years |  | 4 years |  |  |  |  |  |  |
Grant date quoted market price per share | $ / shares | $ / shares | $ 48.9 | $ 44.4 |  |  | $ 53 |  | $ 21.8 |  |  |  |  |  |  |
Stock Appreciation Right Plan For Employees [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Compensation expenses | $ |  |  |  |  |  |  |  |  |  |  | $ 105 | 210 | $ 271 |
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 |  |  |  |  |  |  |  |  |  |  | $ 207 | $ 340 |  |
Unit of cash-settled stock appreciation right | Right |  |  |  |  |  |  |  |  | 1 | 26 |  |  |  |

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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: Share-based payment arrangements [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 2 -IssueDate 2023-01-01 -Paragraph 45 -Subparagraph a -URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2023-en-r&anchor=para_45_a&doctype=Standard -URIDate 2023-03-23 + 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 2023-01-01 -Paragraph 112 -Subparagraph c -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2023-en-r&anchor=para_112_c&doctype=Standard -URIDate 2023-03-23 + 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: Share-based payment arrangements [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 2 -IssueDate 2023-01-01 -Paragraph 51 -Subparagraph b -Clause i -URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2023-en-r&anchor=para_51_b_i&doctype=Standard -URIDate 2023-03-23 + Details
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