Name:	ifrs-full_DisclosureOfTransactionsBetweenRelatedPartiesLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 112
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_112_c&doctype=Standard
-URIDate 2025-03-27

Name:	ifrs-full_GainsOnDisposalsOfInvestmentProperties
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The amount of investments accounted for using the equity method. The equity method is a method of accounting whereby the investment is initially recognised at cost and adjusted thereafter for the post-acquisition change in the investor's share of net assets of the investee. The investor's profit or loss includes its share of the profit or loss of the investee. The investor's other comprehensive income includes its share of the other comprehensive income of the investee. [Refer: At cost [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2025-01-01
-Paragraph 24
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2025-en-r&anchor=para_24_a&doctype=Standard
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2025-01-01
-Paragraph B16
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2025-en-r&anchor=para_B16&doctype=Appendix&subtype=B
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 89
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_89&doctype=Standard
-URIDate 2025-03-27

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 89
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_89&doctype=Standard
-URIDate 2025-03-27

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 54
-Subparagraph e
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_54_e&doctype=Standard
-URIDate 2025-03-27

Name:	ifrs-full_InvestmentAccountedForUsingEquityMethod
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The cash outflow for the purchases of intangible assets, classified as investing activities. [Refer: Intangible assets other than goodwill]

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 7
-IssueDate 2025-01-01
-Paragraph 16
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=7&code=ifrs-tx-2025-en-r&anchor=para_16_a&doctype=Standard
-URIDate 2025-03-27

Name:	ifrs-full_PurchaseOfIntangibleAssetsClassifiedAsInvestingActivities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 24
-IssueDate 2025-01-01
-Paragraph 21
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=24&code=ifrs-tx-2025-en-r&anchor=para_21_a&doctype=Standard
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 234
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_234_a&doctype=Standard
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 234
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_234_a&doctype=Standard
-URIDate 2025-03-27

Name:	ifrs-full_RevenueFromSaleOfGoodsRelatedPartyTransactions
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The amount of current receivables due from related parties. [Refer: Total for all related parties [member]]

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph B9
-Subparagraph b
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_B9_b&doctype=Appendix&subtype=B
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 78
-Subparagraph b
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_78_b&doctype=Standard
-URIDate 2025-03-27

Name:	ifrs-full_TradeAndOtherCurrentReceivablesDueFromRelatedParties
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Acquisition of shares, investments accounted for under the equity method.

No definition available.

Name:	umc_AcquisitionOfSharesInvestmentsAccountedForUnderTheEquityMethod
Namespace Prefix:	umc_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Cash dividends from investees.

No definition available.

Name:	umc_CashDividendsfromInvestees
Namespace Prefix:	umc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Disposal price of subsidiary ownership.

No definition available.

Name:	umc_DisposalPriceOfSubsidiaryOwnership
Namespace Prefix:	umc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Gain loss on disposal of subsidiary ownership.

No definition available.

Name:	umc_GainLossOnDisposalOfSubsidiaryOwnership
Namespace Prefix:	umc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The amount of mask expenditure in related party transactions.

No definition available.

Name:	umc_MaskExpenditureRelatedPartyTransactions
Namespace Prefix:	umc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The amount of other payables of mask expenditure in related party transactions.

No definition available.

Name:	umc_OtherPayablesOfMaskExpenditureRelatedPartyTransactions
Namespace Prefix:	umc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Purchase price for acquisition of a subsidiary's ownership.

No definition available.

Name:	umc_PurchasePriceForAcquisitionOfASubsidiaryOwnership
Namespace Prefix:	umc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Trading capital.

No definition available.

Name:	umc_TradingCapital
Namespace Prefix:	umc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Volume of capital traded.

No definition available.

Name:	umc_VolumeOfCapitalTraded
Namespace Prefix:	umc_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

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

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

Name:	ifrs-full_SignificantInvestmentsInAssociatesAxis=umc_FaradayTechnologyCorpMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	umc_TransactionWithRelatedPartyAxis=umc_FaradayTechnologyCorpMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	umc_TransactionWithRelatedPartyAxis=umc_ArteryTechnologyCorporationLTDMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_CategoriesOfRelatedPartiesAxis=ifrs-full_AssociatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	umc_TransactionWithRelatedPartyAxis=umc_StockOfFaradayMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	umc_TransactionWithRelatedPartyAxis=umc_StockOfUNIMICRONMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_CategoriesOfRelatedPartiesAxis=ifrs-full_OtherRelatedPartiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_CategoriesOfRelatedPartiesAxis=umc_AllOtherRelatedPartiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_CategoriesOfRelatedPartiesAxis=umc_OthersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_CategoriesOfRelatedPartiesAxis=umc_OtherAssociatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_CategoriesOfRelatedPartiesAxis=umc_XiamenJinyuanIndustrialDevelopmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	umc_TransactionWithRelatedPartyAxis=umc_IncreaseOfOwnershipStakeInTheSubsidiaryCompanyUSCXMMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: