Trade and Other Receivables - Impairment Provision (Details) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Reconciliation of changes in allowance account for credit losses of financial assets [abstract]
Impairment provision at period start	€ 2,795
Impairment provision at period end	2,563	€ 2,795
Trade receivables
Reconciliation of changes in allowance account for credit losses of financial assets [abstract]
Impairment provision at period start	2,795	2,787
Allowances	998	915
Amounts applied	(1,019)	(1,044)
Inclusion of companies	14
Translation differences and other	(225)	137
Impairment provision at period end	€ 2,563	€ 2,795

The amount of additional allowance for credit losses of financial assets recognised in profit or loss. [Refer: Allowance account for credit losses of financial assets]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2018-01-01
-Name IFRS
-Number 7
-IssueDate 2017-01-01
-Paragraph 16
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-02&anchor=para_16&doctype=Standard&book=B
-URIDate 2017-03-09

+ Details

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

- Definition

The amount of an allowance account used to record impairments to financial assets due to credit losses. [Refer: Financial assets]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2018-01-01
-Name IFRS
-Number 7
-IssueDate 2017-01-01
-Paragraph 16
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2017-03-02&anchor=para_16&doctype=Standard&book=B
-URIDate 2017-03-09

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The increase (decrease) in an allowance account for credit losses of financial assets resulting from the net exchange differences arising when the financial statements are translated from the functional currency into a different presentation currency, including the translation of a foreign operation into the presentation currency of the reporting entity. [Refer: Allowance account for credit losses of financial assets]

+ References

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- References

No definition available.

+ Details

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- Definition

The decrease in an allowance account for credit losses of financial assets resulting from the reversal of impairment. [Refer: Allowance account for credit losses of financial assets]

+ References

+ Details

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- Definition

Inclusion of Companies for Impairment Provision on Current Trade Receivables

+ References

No definition available.

+ Details

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Namespace Prefix:	tef_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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