Provisions - Spanish Entities - Present Value of Obligations (Details) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of net defined benefit liability (asset) [line items]
Actuarial losses (gains) arising from changes in financial assumptions, net defined benefit liability (asset)	€ (157)
Post-Employment Plans \| Present value of defined benefit obligation
Disclosure of net defined benefit liability (asset) [line items]
Net defined benefit liability (asset) at beginning of period	4,856	€ 4,979	€ 5,077
Net inclusion of entities in the Group	1,563
Current service cost	16	11	12
Interest cost	94	95	105
Pre-retirement cost		6	4
Effect of curtailment/settlement	(2)	(21)	(28)
Benefits paid	(388)	(353)	(327)
Benefits paid due to settlements	(260)
Past service cost		6	4
Actuarial (gains)/losses	57	136	124
Actuarial losses (gains) arising from changes in demographic assumptions, net defined benefit liability (asset)	(7)	15	24
Actuarial losses (gains) arising from changes in financial assumptions, net defined benefit liability (asset)	64	121	100
Exchange differences and other items	(24)	(3)	8
Net defined benefit liability (asset) at end of period	5,912	4,856	4,979
Other similar obligations \| Present value of defined benefit obligation
Disclosure of net defined benefit liability (asset) [line items]
Net defined benefit liability (asset) at beginning of period	1,657	1,813	2,237
Net inclusion of entities in the Group	202
Current service cost	1	1	2
Interest cost	21	27	37
Pre-retirement cost	248	355	213
Effect of curtailment/settlement			(33)
Benefits paid	(490)	(570)	(657)
Benefits paid due to settlements			(1)
Actuarial (gains)/losses	13	6	(8)
Actuarial losses (gains) arising from changes in demographic assumptions, net defined benefit liability (asset)	10	(1)	(12)
Actuarial losses (gains) arising from changes in financial assumptions, net defined benefit liability (asset)	3	7	4
Exchange differences and other items	8	25	23
Net defined benefit liability (asset) at end of period	€ 1,660	€ 1,657	€ 1,813

The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in demographic assumptions that result in remeasurements of the net defined benefit liability (asset). Demographic assumptions deal with matters such as: (a) mortality; (b) rates of employee turnover, disability and early retirement; (c) the proportion of plan members with dependants who will be eligible for benefits; (d) the proportion of plan members who will select each form of payment option available under the plan terms; and (e) claim rates under medical plans. [Refer: Net defined benefit liability (asset)]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 141
-Subparagraph c
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_c_ii&doctype=Standard
-URIDate 2017-03-09

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- Definition

The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) arising from changes in financial assumptions that result in remeasurements of the net defined benefit liability (asset). Financial assumptions deal with items such as: (a) the discount rate; (b) benefit levels, excluding any cost of the benefits to be met by employees, and future salary; (c) in the case of medical benefits, future medical costs, including claim handling costs (ie the costs that will be incurred in processing and resolving claims, including legal and adjuster's fees); and (d) taxes payable by the plan on contributions relating to service before the reporting date or on benefits resulting from that service. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 141
-Subparagraph c
-Clause iii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_c_iii&doctype=Standard
-URIDate 2017-03-09

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- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from employee service in the current period. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 141
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_a&doctype=Standard
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- 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.

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- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from changes in foreign exchange rates. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 141
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_e&doctype=Standard
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- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from the passage of time. [Refer: Interest expense; Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 141
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_b&doctype=Standard
-URIDate 2017-03-09

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- Definition

The amount of deficit or surplus in a defined benefit plan, adjusted for any effect of limiting a net defined benefit asset to the asset ceiling. [Refer: Defined benefit plans [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 140
-Subparagraph a
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- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from past service cost. Past service cost is the change in the present value of the defined benefit obligation for employee service in prior periods, resulting from a plan amendment (the introduction or withdrawal of, or changes to, a defined benefit plan) or a curtailment (a significant reduction by the entity in the number of employees covered by a plan). [Refer: Net defined benefit liability (asset); Defined benefit plans [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 141
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_d&doctype=Standard
-URIDate 2017-03-09

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- Definition

The decrease (increase) in the net defined benefit liability (asset) resulting from payments from the plan. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 141
-Subparagraph g
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141_g&doctype=Standard
-URIDate 2017-03-09

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- Definition

The decrease (increase) in the net defined benefit liability (asset) resulting from payments from the plan in respect of settlements. [Refer: Gains (losses) arising from settlements, net defined benefit liability (asset); Net defined benefit liability (asset); Defined benefit plans [member]]

+ References

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- Definition

The decrease (increase) in a net defined benefit liability (asset) resulting from actuarial gains (losses) that result in remeasurements of the net defined benefit liability (asset).

+ References

No definition available.

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- Definition

Effect of curtailment/settlement on defined benefit liability asset.

+ References

No definition available.

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- Definition

Net inclusion of entities in the Group for defined benefits.

+ References

No definition available.

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- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from pre-retirement cost.

+ References

No definition available.

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