Reserves for Losses and Adjustment Expenses - Reconciliation of Beginning and Ending Consolidated Loss and Loss Adjustment Expenses (LAE) Reserves (Details) - USD ($) $ in Millions |
12 Months Ended | |||||||
|---|---|---|---|---|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
Dec. 31, 2022 |
|||||
| Insurance [Abstract] | ||||||||
| Provision for losses and LAE, beginning balance | $ 8,122.6 | [1] | $ 7,810.6 | $ 7,710.9 | ||||
| Less unpaid losses recoverable from reinsurers at the start of the year | (4,172.0) | (4,577.8) | $ (4,897.7) | |||||
| Net losses and LAE reserves, beginning balance | 3,950.6 | 3,232.8 | 2,813.2 | |||||
| Net incurred losses and loss adjustment expenses related to: | ||||||||
| Current year | 1,654.3 | 1,682.2 | 1,492.2 | |||||
| Prior Year | (107.6) | 35.6 | 60.8 | |||||
| Total incurred | 1,546.7 | 1,717.8 | 1,553.0 | |||||
| Net paid losses and loss adjustment expenses related to: | ||||||||
| Current year | (203.8) | (200.2) | (161.1) | |||||
| Prior years | (939.8) | (741.3) | (1,011.9) | |||||
| Total paid | (1,143.6) | (941.5) | (1,173.0) | |||||
| Foreign exchange losses/(gains) | 89.4 | (58.5) | 39.6 | |||||
| Net Reserves for Losses and LAE | 4,443.1 | 3,950.6 | 3,232.8 | $ 2,813.2 | ||||
| Plus unpaid losses recoverable from reinsurers at the end of the year | 4,281.9 | 4,172.0 | 4,577.8 | |||||
| Reserve for losses and loss adjustment expenses at the end of the year | 8,725.0 | [1] | 8,122.6 | [1] | 7,810.6 | |||
| SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items] | ||||||||
| Reinsurance recoverable on unpaid losses | 4,281.9 | 4,172.0 | ||||||
| Prior Year | $ (107.6) | $ 35.6 | $ 60.8 | |||||
| ||||||||
| X | ||||||||||
- Definition Reinsurance Recoverables Adjustment No definition available.
|
| X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- References No definition available.
|
| X | ||||||||||
- 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
|
| X | ||||||||||
- References No definition available.
|
| X | ||||||||||
- 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/exampleRef
|
| X | ||||||||||
- 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/exampleRef
|
| X | ||||||||||
- 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. No definition available.
|
| X | ||||||||||
- 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
|
| X | ||||||||||
- References No definition available.
|
| X | ||||||||||
- 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/2009/role/commonPracticeRef
|
| X | ||||||||||
- 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
|
| X | ||||||||||
- 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/2009/role/commonPracticeRef
|
| X | ||||||||||
- Definition Amount, after valuation allowance, recoverable under reinsurance contracts including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- 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/exampleRef
|
| X | ||||||||||
- 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/exampleRef
|