The amount of exposure to loss resulting from credit risk. [Refer: Credit risk [member]]

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
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+ Details

Name:	ifrs-full_CreditExposure
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

+ References

No definition available.

+ Details

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

- Definition

The decrease in credit risk on loan commitments and financial guarantee contracts percentage

+ References

No definition available.

+ Details

Name:	san_DecreaseInCreditRiskOnLoanCommitmentsAndFinancialGuaranteeContractsPercentage
Namespace Prefix:	san_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage decrease in nonperforming loans included in exposure to credit risk on loan commitments and financial guarantee contracts.

+ References

No definition available.

+ Details

Name:	san_DecreaseInNonperformingLoansPercent
Namespace Prefix:	san_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The decrease during the period in the nonperforming loans ratio, as a percent.

+ References

No definition available.

+ Details

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Namespace Prefix:	san_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The decrease during the period in the nonperforming loans ratio due to better NPL figure.

+ References

No definition available.

+ Details

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Namespace Prefix:	san_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage exposure to credit risk on loan commitments and financial guarantee contracts.

+ References

No definition available.

+ Details

Name:	san_ExposureToCreditRiskOnLoanCommitmentsAndFinancialGuaranteeContractsPercentage
Namespace Prefix:	san_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The increase during the period in the nonperforming loans ratio attributable to the reduction in lending.

+ References

No definition available.

+ Details

Name:	san_IncreaseInNonperformingLoansRatioDueToReductionInLending
Namespace Prefix:	san_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of instruments classified as non-performing, calculated as the amount of non-performing loans and advances to customers and non-performing contingent liabilities (without country risk) divided by the amount of total loans and advances to customers and contingent liabilities (without country risk).

+ References

No definition available.

+ Details

Name:	san_NonperformingRatio
Namespace Prefix:	san_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

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Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Risk management - Spain Portfolio Overview (Details) - EUR (€) € in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Continental Europe
Credit risk
Credit risk with customers	€ 337,768	€ 331,706	€ 321,395
Spain \| Continental Europe
Credit risk
Credit risk with customers	€ 172,176	€ 172,974	€ 173,032
Total risk exposure (as a percent)	20.70%
Decrease in credit risk on loan commitments and financial guarantee contracts percentage	0.50%
Nonperforming
Credit risk
Credit risk with customers	€ 28,104
Non-performing rate (as a percent)	3.38%
Percentage decrease in non-performing loans ratio	0.55%
Percentage decrease in non-performing loans (NPLs)	16.00%
Nonperforming \| Continental Europe
Credit risk
Non-performing rate (as a percent)	4.50%	5.92%	7.27%
Nonperforming \| Spain \| Continental Europe
Credit risk
Non-performing rate (as a percent)	4.72%	5.41%	6.53%
Percentage decrease in non-performing loans ratio	0.69%
Percentage increase in non-performing loans ratio due to fall in lending	3.00%
Percentage decrease in non-performing loans ratio due to better NPL figure	0.72%
Nonperforming \| Spain \| Non-financial corporations and individual entrepreneurs (Non-financial business activity) \| Continental Europe
Credit risk
Percentage decrease in non-performing loans (NPLs)	19.00%