Financial Assets and Liabilities - Maturity Analysis of Financial Liabilities (Details) - EUR (€) € in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Total Issues	€ 47,375
Loans and other payables	8,900	€ 11,398
Total	52,089	53,440
Telefonica, S.A.
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Debentures and bonds	41,288
Promissory notes & commercial paper	2,406
Total Issues	43,694
Loans and other payables	8,900
Derivative instruments (Note 16)	3,152
Total	55,746	€ 60,361
Telefonica, S.A. \| 2018
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Debentures and bonds	5,313
Promissory notes & commercial paper	2,107
Total Issues	7,420
Loans and other payables	1,714
Derivative instruments (Note 16)	280
Total	9,414
Telefonica, S.A. \| 2019
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Debentures and bonds	3,599
Promissory notes & commercial paper	0
Total Issues	3,599
Loans and other payables	2,250
Derivative instruments (Note 16)	214
Total	6,063
Telefonica, S.A. \| 2020
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Debentures and bonds	5,108
Promissory notes & commercial paper	112
Total Issues	5,220
Loans and other payables	819
Derivative instruments (Note 16)	824
Total	6,863
Telefonica, S.A. \| 2021
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Debentures and bonds	4,760
Promissory notes & commercial paper	0
Total Issues	4,760
Loans and other payables	918
Derivative instruments (Note 16)	453
Total	6,131
Telefonica, S.A. \| 2022
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Debentures and bonds	4,903
Promissory notes & commercial paper	0
Total Issues	4,903
Loans and other payables	531
Derivative instruments (Note 16)	185
Total	5,619
Telefonica, S.A. \| Subsequent years
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Debentures and bonds	17,605
Promissory notes & commercial paper	187
Total Issues	17,792
Loans and other payables	2,668
Derivative instruments (Note 16)	1,196
Total	21,656
Telefonica, S.A. \| Non-current
Disclosure of maturity analysis for non-derivative financial liabilities [line items]
Debentures and bonds	35,975
Promissory notes & commercial paper	299
Total Issues	36,274
Loans and other payables	7,186
Derivative instruments (Note 16)	2,872
Total	€ 46,332

The amount of contractual undiscounted cash flows in relation to bank borrowings. [Refer: Borrowings]

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The amount of contractual undiscounted cash flows in relation to bonds issued. [Refer: Bonds issued]

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The amount of contractual undiscounted cash flows in relation to derivative financial liabilities. [Refer: Derivative financial liabilities]

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The amount of liabilities that are: (a) a contractual obligation: (i) to deliver cash or another financial asset to another entity; or (ii) to exchange financial assets or financial liabilities with another entity under conditions that are potentially unfavourable to the entity; or (b) a contract that will, or may be, settled in the entity’s own equity instruments and is: (i) a non-derivative for which the entity is, or may be, obliged to deliver a variable number of the entity’s own equity instruments; or (ii) a derivative that will, or may be, settled other than by the exchange of a fixed amount of cash or another financial asset for a fixed number of the entity’s own equity instruments. For this purpose, rights, options or warrants to acquire a fixed number of the entity’s own equity instruments for a fixed amount of any currency are equity instruments if the entity offers the rights, options or warrants pro rata to all of its existing owners of the same class of its own non-derivative equity instruments. Also, for those purposes the entity’s own equity instruments do not include puttable financial instruments that are classified as equity instruments in accordance with paragraphs 16A-16B of IAS 32, instruments that impose on the entity an obligation to deliver to another party a pro rata share of the net assets of the entity only on liquidation and are classified as equity instruments in accordance with paragraphs 16C-16D of IAS 32, or instruments that are contracts for the future receipt or delivery of the entity’s own equity instruments. As an exception, an instrument that meets the definition of a financial liability is classified as an equity instrument if it has all the features and meets the conditions in paragraphs 16A-16B or paragraphs 16C-16D of IAS 32. [Refer: Financial instruments, class [member]; Financial assets; Derivatives [member]]

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