Loss and loss adjustment expense reserves - Narrative (Details) $ in Millions |
3 Months Ended | 6 Months Ended | ||||||
|---|---|---|---|---|---|---|---|---|
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Jun. 30, 2026
USD ($)
|
Jun. 30, 2025
USD ($)
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Jun. 30, 2026
USD ($)
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Jun. 30, 2025
USD ($)
|
Dec. 31, 2025
USD ($)
|
Dec. 31, 2023
USD ($)
|
Jun. 30, 2023
USD ($)
|
Sep. 30, 2022
USD ($)
|
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| Disposal Group, Including Discontinued Operations [Line Items] | ||||||||
| Prior year loss reserve development | $ (15.0) | $ (8.7) | $ (32.9) | $ (42.9) | ||||
| Loss reserves | $ 400.0 | $ 905.6 | $ 1,300.0 | |||||
| Funds held liability | 175.7 | 175.7 | ||||||
| Reinsurance balances payable | $ 1,461.3 | $ 1,461.3 | $ 1,447.6 | |||||
| 2024 LPT | ||||||||
| Disposal Group, Including Discontinued Operations [Line Items] | ||||||||
| Aggregate limit, percentage of booked reserves | 1.50 | 1.50 | ||||||
| 2023 LPT | ||||||||
| Disposal Group, Including Discontinued Operations [Line Items] | ||||||||
| Aggregate limit, percentage of booked reserves | 1.30 | 1.30 | ||||||
| Pallas Reinsurance Company Ltd. | ||||||||
| Disposal Group, Including Discontinued Operations [Line Items] | ||||||||
| Reinsurance balances payable | $ 297.6 | $ 297.6 | ||||||
| Reinsurance recoverable | $ 305.4 | $ 305.4 | ||||||
| X | ||||||||||
- Definition Reinsurance, Loss Portfolio Transfer, Aggregate Limit, Percentage Of Booked Reserves No definition available.
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- Definition Reinsurance, Loss Portfolio Transfer, Loss Reserves Covered No definition available.
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- Definition Amount of funds held as security for payments to be received under reinsurance contracts. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- 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
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- Definition The carrying amount as of the balance sheet date of the known and estimated amounts owed to insurers under reinsurance treaties or other arrangements. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount before valuation allowance recoverable 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/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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