Defined Benefit Plans - Summary of Actuarial Assumptions Used to Determine Defined Benefit Obligations (Parenthetical) (Detail) - Transamerica [member] |
Dec. 31, 2025 |
Dec. 31, 2024 |
|---|---|---|
| Pension defined benefit plans [member] | ||
| Disclosure of sensitivity analysis for actuarial assumptions [Line Items] | ||
| Discount rate | 5.45% | 5.59% |
| Post retirement welfare plan [member] | ||
| Disclosure of sensitivity analysis for actuarial assumptions [Line Items] | ||
| Discount rate | 5.23% | 5.51% |