Related Party Transactions - Summary of Transactions with Related Party Pension Plans (Detail) - EUR (€) € in Millions |
Dec. 31, 2025 |
Dec. 31, 2024 |
|---|---|---|
| Related party transactions [abstract] | ||
| Equity shares issued by the Group held in plan assets | € 0 | € 0 |
| Other assets | 1 | 2 |
| Fees paid from plan assets to asset managers of the Group | 16 | 16 |
| Market value of derivatives with a counterparty of the Group | 411 | 679 |
| Notional amount of derivatives with a counterparty of the Group | € 8,885 | € 9,730 |