Reinsurance - Summary of Assumed and Ceded Reinsurance on Premiums Written, Premiums Earned and Insurance Losses and Loss Adjustment Expenses (Details) - USD ($) $ in Millions |
12 Months Ended | ||||
|---|---|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
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| Premiums written: | |||||
| Insurance | $ 2,768.1 | $ 2,723.5 | $ 2,446.6 | ||
| Reinsurance | 1,905.1 | 1,885.8 | 1,521.0 | ||
| Ceded | (1,837.2) | (1,666.7) | (1,385.7) | ||
| Net written premiums | 2,836.0 | 2,942.6 | 2,581.9 | ||
| Premiums earned: | |||||
| Insurance | 2,752.2 | 2,565.7 | 2,444.8 | ||
| Reinsurance | 1,850.0 | 1,822.1 | 1,562.0 | ||
| Ceded | (1,770.3) | (1,498.1) | (1,392.3) | ||
| Net premiums earned | [1] | 2,831.9 | 2,889.7 | 2,614.5 | |
| Losses and loss adjustment expenses: | |||||
| Insurance | (1,647.2) | (1,759.1) | (1,644.5) | ||
| Reinsurance | (985.9) | (915.8) | (707.2) | ||
| Ceded | 1,086.4 | 957.1 | 798.7 | ||
| Losses and loss adjustment expenses | [1] | $ (1,546.7) | $ (1,717.8) | $ (1,553.0) | |
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- Definition Amount of earned premiums assumed from other entities. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of written premiums assumed from other entities. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of earned premiums ceded to other entities. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of written premiums ceded to other entities. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums earned. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums written. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount, before effect of policies assumed or ceded, of expense related to provision for policy benefits and costs incurred. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount, after effects of policies assumed or ceded, of expense related to the provision for policy benefits and costs incurred. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- References No definition available.
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- Definition Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums written. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- References No definition available.
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- Definition Amount of policy benefits and costs incurred for policies assumed. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount of reduction of provision for policy benefits and costs incurred for policies ceded. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- References No definition available.
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