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

The amount of liabilities that are subordinate to other liabilities with respect to claims.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 55
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_55&doctype=Standard
-URIDate 2025-03-27

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

New liabilities assumed during the reporting period that are subordinated to claims of general creditors.

No definition available.

Name:	san_AdditionsSubordinatedLiabilities
Namespace Prefix:	san_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The increase (decrease) in subordinated liabilities due to exchange differences and other movements.

No definition available.

Name:	san_SubordinatedLiabilitiesIncreaseDecreaseDueToExchangeDifferencesAndOtherMovements
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Subordinated Liabilities, Interest Paid In Remuneration Of Issuances

No definition available.

Name:	san_SubordinatedLiabilitiesInterestPaidInRemunerationOfIssuances
Namespace Prefix:	san_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Subordinated Liabilities, Net Inclusion Of Entities

No definition available.

Name:	san_SubordinatedLiabilitiesNetInclusionOfEntities
Namespace Prefix:	san_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The net amount of issuances, redemptions and repurchases for subordinated liabilities.

No definition available.

Name:	san_SubordinatedLiabilitiesNetIssuancesRedemptionsAndRepurchases
Namespace Prefix:	san_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Subordinated Liabilities, Net Redemptions And Repurchases

No definition available.

Name:	san_SubordinatedLiabilitiesNetRedemptionsAndRepurchases
Namespace Prefix:	san_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Name:	ifrs-full_CategoriesOfFinancialLiabilitiesAxis=ifrs-full_FinancialLiabilitiesAtAmortisedCostCategoryMember
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Balance Type:
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Name:	ifrs-full_SignificantInvestmentsInSubsidiariesAxis=san_BancoSantanderBrasilSAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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

Name:	ifrs-full_SignificantInvestmentsInSubsidiariesAxis=san_SantanderUKGroupHoldingsPLCMember
Namespace Prefix:
Data Type:	na
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Name:	ifrs-full_SignificantInvestmentsInSubsidiariesAxis=san_SantanderBankPolskaSAMember
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Data Type:	na
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Period Type:

Name:	ifrs-full_SignificantInvestmentsInSubsidiariesAxis=san_SantanderUKPLCMember
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