Employee benefit obligations - Schedule of amounts recognized for the legacy SES postretirement benefit plan (Detail) - EUR (€) € in Millions |
5 Months Ended | 12 Months Ended | |
|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2025 |
Dec. 31, 2024 |
|
| Disclosure Of amounts recognized for the legacy SES postretirement benefit plan [Line Items] | |||
| Benefit Payments From The Plan | € 0 | ||
| Interest expense | 6 | ||
| Interest income | (6) | ||
| SES postretirement benefit plan [Member] | |||
| Disclosure Of amounts recognized for the legacy SES postretirement benefit plan [Line Items] | |||
| Accumulated Projected Benefit Obligation (APBO) Beginning Period | € 7 | € 6 | |
| Benefit Payments From The Plan | (1) | (1) | |
| Actuarial loss (gain) | 0 | 2 | |
| Interest expense | 0 | 0 | |
| Interest income | 0 | 0 | |
| Accumulated Projected Benefit Obligation (APBO) end of year | € 6 | € 6 | € 7 |