Defined Benefit Plans - Summary of Fair Value of Plan Assets (Detail) - EUR (€) € in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
|
| Disclosure of net defined benefit liability (asset) [Line Items] | ||
| Current year service cost | € 43 | € 39 |
| Net interest on net defined benefit liability (asset) | 18 | 18 |
| Total defined benefit expenses | 61 | 57 |
| Retirement Benefit Plans [member] | ||
| Disclosure of net defined benefit liability (asset) [Line Items] | ||
| Current year service cost | 36 | 32 |
| Net interest on net defined benefit liability (asset) | 9 | 9 |
| Total defined benefit expenses | 45 | 42 |
| Other Post Employment Benefit Plans [member] | ||
| Disclosure of net defined benefit liability (asset) [Line Items] | ||
| Current year service cost | 7 | 7 |
| Net interest on net defined benefit liability (asset) | 9 | 9 |
| Total defined benefit expenses | € 15 | € 15 |