Reserves for Losses and Loss Adjustment Expenses - Schedule of Reconciliation of Unpaid Losses and Loss Adjustment Expenses (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||||
|---|---|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
Dec. 31, 2025 |
Dec. 31, 2024 |
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| Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] | ||||||
| Reserves for losses and loss adjustment expenses, beginning of period | $ 2,607.1 | $ 3,134.3 | ||||
| Reinsurance recoverable on reserves for losses and loss adjustment expenses | $ (1,312.4) | $ (1,131.8) | (1,312.4) | (1,131.8) | $ (1,195.6) | $ (1,255.6) |
| Net reserves for losses and loss adjustment expenses, beginning of period | 1,411.5 | 1,878.7 | ||||
| Current year | 347.2 | 196.7 | 899.4 | 874.2 | ||
| Prior years | 4.7 | (16.0) | (31.1) | 32.4 | ||
| Total incurred | 351.9 | 180.7 | 868.3 | 906.6 | ||
| Current year | (65.5) | (265.7) | ||||
| Prior years | (587.6) | (1,355.3) | ||||
| Total paid | (653.1) | (1,621.0) | ||||
| Foreign exchange | (8.5) | 25.3 | ||||
| Net reserves for losses and loss adjustment expenses, end of period | 1,618.2 | 1,189.6 | 1,618.2 | 1,189.6 | ||
| Reinsurance recoverable on reserves for losses and loss adjustment expenses | 1,312.4 | 1,131.8 | 1,312.4 | 1,131.8 | $ 1,195.6 | $ 1,255.6 |
| Reserves for losses and loss adjustment expenses, end of period | $ 2,930.6 | $ 2,321.4 | $ 2,930.6 | $ 2,321.4 | ||
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- Definition The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount, after effects of reinsurance, of payments to settle claims incurred in the current period and related claims settlement costs. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount, after effects of reinsurance, of payments to settle claims incurred in prior periods and related claims settlement costs. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of foreign currency gain (loss) which decreases (increases) the cost of settling unpaid claims after deduction of reinsurance recoveries. Includes, but is not limited to, claims which have been incurred but not reported. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount, after effects of reinsurance, of expense (reversal of expense) for claims incurred and costs incurred in the claim settlement process. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Liability as of the balance sheet date for amounts representing estimated cost of settling unpaid claims under the terms of the underlying insurance policies, less estimated reinsurance recoveries on such claims. This includes an estimate for claims which have been incurred but not reported. Claim adjustment expenses represent the costs estimated to be incurred in the settlement of unpaid claims. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. No definition available.
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- Definition Amount, after effects of reinsurance, of payments to settle insured claims and pay costs incurred in the claims settlement process. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount, after valuation allowance, recoverable under reinsurance contracts for losses reported to the ceding insurer but not yet paid and amounts expected for incurred losses and settlement expenses, which have not yet been reported to the ceding insurer. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount, after effects of reinsurance, of expense for claims incurred in the current reporting period and related claims settlement costs. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount, after effects of reinsurance, of expense (reversal of expense) for claims incurred in prior reporting periods and related claims settlement costs. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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