Customer deposits - Schedule of customer deposits (Details) - EUR (€) € in Millions	Jun. 30, 2025	Dec. 31, 2024
Deposits from customers [abstract]
Current accounts / Overnight deposits	€ 232,153	€ 227,827
Savings accounts	379,403	354,560
Time deposits	120,143	107,695
Other	6,329	1,579
Customer deposits	€ 738,028	€ 691,661

The amount of balances in customers' deposit accounts held by the entity that the entity does not separately disclose in the same statement or note.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2024-01-01
-Paragraph 112
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2024-en-r&anchor=para_112_c&doctype=Standard
-URIDate 2024-03-27

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