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Contents of Significant Accounts - Refund Liabilities - Summary of Refund Liabilities (classified under other current liabilities) (Detail) - TWD ($) $ in Thousands | Dec. 31, 2024 | Dec. 31, 2023
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Disclosure Of Refund Liability [Abstract] |  |
Refund liabilities | $ 3,918,437 | $ 3,033,576

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- Definition Disclosure of refund liability [abstract] + References No definition available. + Details
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Namespace Prefix: | umc_
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Balance Type: | na
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- Definition Refund liabilities. + References No definition available. + Details
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Period Type: | instant