Related party transactions - Narrative (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 |
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| Related Party Transaction [Line Items] | |||||
| Premiums written, gross | $ 994.9 | $ 874.4 | $ 2,976.0 | $ 2,807.3 | |
| Insurance and reinsurance balances receivable, net | 2,558.9 | 2,558.9 | $ 2,260.3 | ||
| Reinsurance balances payable | 1,472.5 | 1,472.5 | 1,447.6 | ||
| Related Party | |||||
| Related Party Transaction [Line Items] | |||||
| Premiums written, gross | 25.1 | $ 42.2 | 81.5 | $ 53.9 | |
| Insurance and reinsurance balances receivable, net | 83.8 | 83.8 | 86.4 | ||
| Reinsurance balances payable | $ 0.0 | $ 0.0 | $ 0.0 | ||
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- Definition The carrying amount as of the balance sheet date due the entity from (a) agents and insureds, (b) uncollected premiums and (c) others, net of the allowance for doubtful accounts. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount of direct and assumed premiums written. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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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 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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- Details
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