Shareholders' Equity and Other Equity Instruments - Summary of Revaluation Reserve for Investments Measured at FVOCI (Detail) - EUR (€) € in Millions |
Jun. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Disclosure of revaluation reserve [Line Items] | ||
| Revaluation reserve for investments measured at FVOCI | € (3,097) | € (2,434) |
| Shares [member] | ||
| Disclosure of revaluation reserve [Line Items] | ||
| Revaluation reserve for investments measured at FVOCI | 3 | 3 |
| Debt securities [member] | ||
| Disclosure of revaluation reserve [Line Items] | ||
| Revaluation reserve for investments measured at FVOCI | (3,094) | (2,431) |
| Money market and other short-term investments [member] | ||
| Disclosure of revaluation reserve [Line Items] | ||
| Revaluation reserve for investments measured at FVOCI | € (6) | € (6) |