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Reinsurance (Narrative) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Reinsurance Disclosures [Line Items] |  |  |
Percentage of ceded earned premiums to gross earned premiums | 44.00% | 39.00% | 38.00%
Percentage of assumed earned premiums to net earned premiums | 38.00% | 31.00% | 30.00%
Underwriting [Member] |  |  |
Reinsurance Disclosures [Line Items] |  |  |
Reinsurance recoverables | $ (1,917,318) | $ (1,496,265) | $ (834,648)
Reinsurance Recoverables, Gross | $ 5,000,000 | $ 4,000,000 |
Underwriting [Member] | Ten Largest Reinsurers [Member] |  |  |
Reinsurance Disclosures [Line Items] |  |  |
Recoverable balances as a percentage of the total balance | 63.00% | 65.00% |
Underwriting [Member] | RenaissanceRe |  |  |
Reinsurance Disclosures [Line Items] |  |  |
Recoverable balances as a percentage of the total balance | 19.00% |  |
Fronting [Member] |  |  |
Reinsurance Disclosures [Line Items] |  |  |
Reinsurance recoverables | $ 3,500,000 | $ 2,500,000 | $ 3,000,000
Program Services [Member] |  |  |
Reinsurance Disclosures [Line Items] |  |  |
Reinsurance Recoverables, Gross | $ 6,000,000 | $ 4,900,000 |
Program Services [Member] | Ten Largest Reinsurers [Member] |  |  |
Reinsurance Disclosures [Line Items] |  |  |
Recoverable balances as a percentage of the total balance | 55.00% | 56.00% |
Program Services [Member] | Knight Insurance Company |  |  |
Reinsurance Disclosures [Line Items] |  |  |
Recoverable balances as a percentage of the total balance | 9.00% |  |
ILS fronting [Member] | Nephila Reinsurers [Member] |  |  |
Reinsurance Disclosures [Line Items] |  |  |
Recoverable balances as a percentage of the total balance | 100.00% |  |

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