Distribution of the Bank's profit, etc. - EPS Basic (Details) - EUR (€) € / shares in Units, € in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basic earnings per share [abstract]
Profit (loss), attributable to owners of parent	€ 6,619	€ 6,204	€ 5,966
Remuneration of contingently convertible preference shares (PPC) (millions of euros)	(395)	(334)	(276)
Net profit for the year	6,224	5,870	5,690
Profit or Loss from continuing operations (net of non-controlling interests) (millions of euros)	€ 6,224	€ 5,870	€ 5,690
Weighted average number of shares outstanding	15,394,458,789	14,656,359,963	14,349,578,605
Total basic earnings (loss) per share	€ 0.404	€ 0.401	€ 0.397
Basic earnings per share from discontinued operations (euros)	0.000	0.000	0.000
Basic earnings per share from continuing operations (euros)	€ 0.404	€ 0.401	€ 0.397

The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator) divided by the weighted average number of ordinary shares outstanding during the period (the denominator).

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Basic earnings (loss) per share from discontinued operations. [Refer: Basic earnings (loss) per share; Discontinued operations [member]]

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The increase (decrease) in equity resulting from the conversion of convertible instruments.

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The profit (loss) attributable to ordinary equity holders of the parent equity. [Refer: Profit (loss)]

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The profit (loss) attributable to owners of the parent. [Refer: Profit (loss)]

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The profit (loss) from continuing operations attributable to ordinary equity holders of the parent equity, adjusted for the effects of all dilutive potential ordinary shares. [Refer: Profit (loss) from continuing operations]

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The number of ordinary shares outstanding at the beginning of the period, adjusted by the number of ordinary shares bought back or issued during the period multiplied by a time-weighting factor.

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