Provisions - Main Actuarial Assumptions Used in Telefónica United Kingdom Pension Plan (Details) - Telefónica United Kingdom - Foreign defined benefit plans	12 Months Ended
Dec. 31, 2017 year beneficiary	Dec. 31, 2016 beneficiary
Disclosure of defined benefit plans [line items]
Number of beneficiaries under plan \| beneficiary	4,491	4,532
Average duration of plans \| year	23
Nominal rate of pension payment increase	3.15%	3.15%
Discount rate	2.45%	2.60%
Expected inflation	3.30%	3.35%

The discount rate used as the significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit obligation, at present value; Actuarial assumptions [member]]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 144
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_144&doctype=Standard
-URIDate 2017-03-09

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- Definition

The expected rate of inflation that is used as a significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit plans [member]; Defined benefit obligation, at present value; Actuarial assumptions [member]]

+ References

+ Details

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- Definition

The expected rate of increases in pension that is used as a significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit plans [member]; Defined benefit obligation, at present value; Actuarial assumptions [member]]

+ References

+ Details

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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 weighted average duration of a defined benefit obligation. [Refer: Weighted average [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 147
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_147_c&doctype=Standard
-URIDate 2017-03-09

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- Definition

Number Of Beneficiaries

+ References

No definition available.

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- Details

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- Details

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