Capital and funding - Disclosure of Fair Value Reserve (Details) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024
Equity and liabilities [abstract]
Fair value reserve at beginning of period	€ 600	€ 392
Gains/(losses) on equity instruments	(14)	60
Gains/(losses) on cash flow hedges	(196)	210
Hedging (gains)/losses transferred to non-financial assets	(58)	(62)
Fair value reserve at end of period	€ 332	€ 600

A component of equity representing the reserve of gains and losses on financial assets measured at fair value through other comprehensive income. [Refer: Financial assets measured at fair value through other comprehensive income; Other comprehensive income]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 78
-Subparagraph e
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_78_e&doctype=Standard
-URIDate 2025-03-27

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