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v3.26.1

Primary and secondary segments reporting - Primary segments, narrative (Details) | 12 Months Ended
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Dec. 31, 2025 operatingAreas segment
Disclosure of operating segments [abstract] |
Number of operating segments | segment | 6
Number of operating areas | operatingAreas | 5

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- References No definition available. + Details
Name: | ifrs-full_DisclosureOfOperatingSegmentsAbstract
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Represents the number of operating areas. + References No definition available. + Details
Name: | san_NumberOfOperatingAreas
Namespace Prefix: | san_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

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- Definition Reportable Segments, Number + References No definition available. + Details
Name: | san_ReportableSegmentsNumber
Namespace Prefix: | san_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration