Financial instruments - Summary of Fair Values of Financial Assets and Financial Liabilities (Details) - EUR (€) € in Millions	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024
Financial assets
Cash and cash equivalents	€ 4,344	€ 6,136	€ 4,970
Financial assets at amortised cost	945	1,262	1,395
Financial assets at fair value through other comprehensive income	537	600	586
Financial assets	7,037	9,037	7,921
Derivatives
Financial assets
Financial assets at fair value through profit or loss	360	217	118
Other
Financial assets
Financial assets at fair value through profit or loss	851	822	852
Fair value
Financial assets
Cash and cash equivalents	4,344	6,136	4,970
Financial assets at amortised cost	945	1,262	1,395
Financial assets at fair value through other comprehensive income	537	600	586
Financial assets	7,037	9,037	7,921
Financial liabilities
Bank loans and overdrafts	(529)	(521)	(460)
Bonds and other loans	(28,696)	(28,037)	(27,836)
Lease liabilities	(1,524)	(1,486)	(1,358)
Derivatives	(614)	(594)	(537)
Other financial liabilities	(189)	(804)	(570)
Financial liabilities	(31,552)	(31,442)	(30,761)
Fair value \| Derivatives
Financial assets
Financial assets at fair value through profit or loss	360	217	118
Fair value \| Other
Financial assets
Financial assets at fair value through profit or loss	851	822	852
Carrying amount
Financial assets
Cash and cash equivalents	4,344	6,136	4,970
Financial assets at amortised cost	945	1,262	1,395
Financial assets at fair value through other comprehensive income	537	600	586
Financial assets	7,037	9,037	7,921
Financial liabilities
Bank loans and overdrafts	(529)	(521)	(460)
Bonds and other loans	(29,169)	(28,648)	(28,729)
Lease liabilities	(1,524)	(1,486)	(1,358)
Derivatives	(614)	(594)	(537)
Other financial liabilities	(189)	(804)	(570)
Financial liabilities	(32,025)	(32,053)	(31,654)
Carrying amount \| Derivatives
Financial assets
Financial assets at fair value through profit or loss	360	217	118
Carrying amount \| Other
Financial assets
Financial assets at fair value through profit or loss	€ 851	€ 822	€ 852

The amount of cash on hand and demand deposits, along with short-term, highly liquid investments that are readily convertible to known amounts of cash and that are subject to an insignificant risk of changes in value. [Refer: Cash; Cash equivalents]

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The amount of financial liabilities classified as derivative instruments. [Refer: Financial assets; Derivatives [member]]

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The amount of assets that are: (a) cash; (b) an equity instrument of another entity; (c) a contractual right: (i) to receive cash or another financial asset from another entity; or (ii) to exchange financial assets or financial liabilities with another entity under conditions that are potentially favourable to the entity; or (d) 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 receive 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 the entity’s own equity instruments do not include puttable financial instruments 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. [Refer: Classes of financial instruments [domain]; Financial liabilities]

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The amount of financial assets at amortised cost. The amortised cost is the amount at which financial assets are measured at initial recognition minus principal repayments, plus or minus the cumulative amortisation using the effective interest method of any difference between that initial amount and the maturity amount, and adjusted for any impairment. [Refer: Financial assets]

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The amount of financial assets at fair value through other comprehensive income. [Refer: At fair value [member]; Financial assets; Other comprehensive income]

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The amount of financial assets that are measured at fair value and for which gains (losses) are recognised in profit or loss. A financial asset shall be measured at fair value through profit or loss unless it is measured at amortised cost or at fair value through other comprehensive income. A gain (loss) on a financial asset measured at fair value shall be recognised in profit or loss unless it is part of a hedging relationship, it is an investment in an equity instrument for which the entity has elected to present gains and losses in other comprehensive income or it is a financial asset measured at fair value through other comprehensive income. [Refer: At fair value [member]; Financial assets]

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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: Classes of financial instruments [domain]; Financial assets; Derivatives [member]]

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The amount of liabilities related to the entity's leases. Lease is a contract, or part of a contract, that conveys the right to use an underlying asset for a period of time in exchange for consideration.

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The amount of financial liabilities that the entity does not separately disclose in the same statement or note. [Refer: Financial liabilities]

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Bank loans and overdrafts.

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Bonds and other loans.

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