Derivative financial instruments and hedge accounting - Underlying asset or liability by type of risk hedged under cash flow hedge (Details) - Other cash flow derivatives - EUR (€) € in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Commodity price risk \| Planned sales
Cash flow hedges [abstract]
Change of the underlying asset used for the calculation of hedging ineffectivenes	€ (600)	€ 1,023
CFH reserve	10	(850)
Reclassification adjustments	(233)	(123)
Interest rate risk \| Hedged flows
Cash flow hedges [abstract]
Change of the underlying asset used for the calculation of hedging ineffectivenes	(26)	12
CFH reserve	€ 24	€ (12)

The gain (loss) on the change in fair value of the hedged item used as a basis for recognising hedge ineffectiveness. Hedge ineffectiveness is the extent to which the changes in the fair value or the cash flows of the hedging instrument are greater or less than those on the hedged item.