Income Taxes - Additional Information (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
|
| Income Taxes | ||
| Unremitted earnings of subsidiaries | $ 18,700.0 | $ 16,200.0 |
| Allied World, Falcon and Farmers Edge | ||
| Income Taxes | ||
| Unused losses which generate the deferred income tax assets not recorded | 169.1 | 208.1 |
| Canada | ||
| Income Taxes | ||
| Unused losses which generate the deferred income tax assets not recorded | 2,134.3 | 2,016.5 |
| Europe | ||
| Income Taxes | ||
| Unused losses which generate the deferred income tax assets not recorded | 732.1 | 703.6 |
| United States | ||
| Income Taxes | ||
| Unused losses which generate the deferred income tax assets not recorded | $ 355.8 | 375.6 |
| Switzerland | Allied World | ||
| Income Taxes | ||
| Operating loss carryforward, expiration period | 7 years | |
| Operating and capital losses | ||
| Income Taxes | ||
| Deferred income tax assets not recorded | $ 935.9 | $ 965.7 |