Other Equity Instruments - Summary of Other Equity Instruments (Detail) - EUR (€) € in Millions |
6 Months Ended | |
|---|---|---|
Jun. 30, 2026 |
Dec. 31, 2025 |
|
| Junior Perpetual Capital Securities [member] | ||
| Disclosure of other equity instruments [line items] | ||
| Decrease In Other Equity Instruments Through Tender Offers | € 217 | |
| Perpetual Cumulative Subordinated Bonds [member] | ||
| Disclosure of other equity instruments [line items] | ||
| Decrease In Other Equity Instruments Through Tender Offers | 157 | |
| Junior Perpetual Capital Securities and Perpetual Cumulative Subordinated Bonds [Member] | ||
| Disclosure of other equity instruments [line items] | ||
| Other Equity Instruments Outstanding Amount | € 1,003 | € 1,377 |