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Contents of Significant Accounts - Summary of Income Recognized in Profit or Loss from Equity Instruments Designated as Fair Value Through Other Comprehensive Income (Detail) - TWD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023
Dividend Income [Abstract] |  |
Held at end of period | $ 888,826 | $ 1,052,336
Derecognized during the period | 0 | 142,535
Total | $ 888,826 | $ 1,194,871

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- Definition The amount of dividends related to investments in equity instruments that the entity has designated at fair value through other comprehensive income, derecognised during the reporting period. [Refer: Investments in equity instruments designated at fair value through other comprehensive income [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2024-01-01 -Paragraph 11A -Subparagraph d -URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2024-en-r&anchor=para_11A_d&doctype=Standard -URIDate 2024-03-27 + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition The amount of dividends related to investments in equity instruments that the entity has designated at fair value through other comprehensive income, held at the end of the reporting period. [Refer: Investments in equity instruments designated at fair value through other comprehensive income [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2024-01-01 -Paragraph 11A -Subparagraph d -URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2024-en-r&anchor=para_11A_d&doctype=Standard -URIDate 2024-03-27 + Details
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- Definition Dividend income. + References No definition available. + Details
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Namespace Prefix: | umc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition The amount of dividends related to investments in equity instruments that the entity has designated at fair value through other comprehensive income, held at the end of the reporting period and derecognised during the reporting period. + References No definition available. + Details
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Namespace Prefix: | umc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant