Retroactive reinsurance - Reconciliation of changes in claim liabilities and incurred losses and loss adjustment expenses (Detail) - Retroactive Reinsurance [Member] - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
|
| Liability for Claims and Claims Adjustment Expense [Line Items] | |||
| Gross liabilities at the beginning of the year | $ 32,443 | $ 34,647 | $ 35,415 |
| Losses and LAE incurred | 954 | 945 | 1,484 |
| Losses and LAE paid | (1,776) | (2,399) | (1,934) |
| Foreign currency effect | 120 | (52) | 57 |
| Gross liabilities at end of year | 31,048 | 32,443 | 34,647 |
| Unpaid Losses and Loss Adjustment Expenses [Member] | |||
| Liability for Claims and Claims Adjustment Expense [Line Items] | |||
| Losses and LAE incurred | 261 | 247 | 1,109 |
| Deferred Charges Reinsurance Assumed [Member] | |||
| Liability for Claims and Claims Adjustment Expense [Line Items] | |||
| Losses and LAE incurred | $ 693 | $ 698 | $ 375 |