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Summary of Material Accounting Policies - Consolidated Entities (Parenthetical) (Detail)	1 Months Ended
	Aug. 31, 2024
UNITEDDS SEMICONDUCTOR (SHANDONG) CO., LTD. (UDS) [member]
Disclosure of subsidiaries [line items]
Disposal of ownership interest in subsidiary	100.00%

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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

Disposal of ownership interest in subsidiary.

+ References

No definition available.

+ Details

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Namespace Prefix:	umc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

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- Details

Name:	ifrs-full_SignificantInvestmentsInSubsidiariesAxis=umc_UnitedDSSemiconductorShandongCoLtdUDSMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: