Note 12 - Changes in fair value of financial assets attributable to movements in counterparty credit risk (Detail) - Changes in fair value of of financial assets attributable to movements in couterparty credit risk [Member] - EUR (€) € in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Changes in fair value of financial assets attributable to movements in couterparty credit risk [line items]
Notional value of financial assets exposed to credit risk	€ 75	€ 168
Annual change in the fair value reflected in the Statement of Income	1	0
Cumulative change in the fair value	0	1
Notional of credit derivatives used to mitigate credit risk	40	90
Annual change in the fair value reflected in the Statement of Income	0	0
Cumulative change in the fair value	€ 1	€ 0