Basis of preparation - Borrowing costs (Details) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024
Corporate information and statement of IFRS compliance [abstract]
Borrowing costs capitalised	€ 317	€ 324

The amount of interest and other costs that an entity incurs in connection with the borrowing of funds that are directly attributable to the acquisition, construction or production of a qualifying asset and which form part of the cost of that asset.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 23
-IssueDate 2025-01-01
-Paragraph 26
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=23&code=ifrs-tx-2025-en-r&anchor=para_26_a&doctype=Standard
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 225
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_225_a&doctype=Standard
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 225
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_225_a&doctype=Standard
-URIDate 2025-03-27

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