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v3.26.1

Share premium (Details) - EUR (€) € in Millions | 12 Months Ended
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Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023
Share Premium [Abstract] |  |  |
Decrease in net issue premium | € 3,055 | € 3,778 | € 1,595
Redemption of treasury shares, purchase value | 3,287 | 4,294 | 1,900
Redemption of treasury shares, par value | € 231 | € 516 | € 305

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- Definition Increase (Decrease) In Net Issue Premium + References No definition available. + Details
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- Definition Redemption Of Treasury Shares, Par Value + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Redemption Of Treasury Shares, Purchase Value + References No definition available. + Details
Name: | san_RedemptionOfTreasurySharesPurchaseValue
Namespace Prefix: | san_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition N/A + References No definition available. + Details
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Namespace Prefix: | san_
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