Shareholders' Equity - Summary of Revaluation Reserve for Investments Measured at FVOCI (Detail) - EUR (€) € in Millions |
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
|---|---|---|---|
| Disclosure of revaluation reserve [Line Items] | |||
| Revaluation reserve for investments measured at FVOCI | € (2,434) | € (4,426) | € (3,300) |
| Shares [member] | |||
| Disclosure of revaluation reserve [Line Items] | |||
| Revaluation reserve for investments measured at FVOCI | 3 | 3 | 2 |
| Debt securities [member] | |||
| Disclosure of revaluation reserve [Line Items] | |||
| Revaluation reserve for investments measured at FVOCI | (2,431) | (4,425) | (3,297) |
| Money market and other short-term investments [member] | |||
| Disclosure of revaluation reserve [Line Items] | |||
| Revaluation reserve for investments measured at FVOCI | € (6) | € (5) | € (5) |