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Reserve for Loss and Loss Expense - Narrative (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Increase of net loss and loss expense reserves | $ 849,200 | $ 331,000 | $ 385,000
Salvage and subrogation recoveries, value | 133,700 | 116,000 | 91,300
Incurred loss and loss expense for claims occurring in the prior year | 285,271 | 9,954 | (78,890)
Favorable or Unfavorable Loss Development |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Incurred loss and loss expense for claims occurring in the prior year | 285,300 | 10,000 | (78,900)
Favorable or Unfavorable Loss Development | Casualty lines |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Incurred loss and loss expense for claims occurring in the prior year | 311,000 | (6,500) | (86,000)
Favorable or Unfavorable Loss Development | Property lines |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Incurred loss and loss expense for claims occurring in the prior year | $ (25,700) | $ 16,500 | $ 7,100

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- Definition Amount of increase (decrease) in liability 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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Subparagraph (a) -SubTopic 10 -Topic 230 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-28 + Details
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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. + References No definition available. + Details
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- Definition The estimated amount as of the balance sheet date to be received by an insurer from the sale of property (usually damaged) on which the insurer has paid a total claim to the insured and has obtained title to the property and the right of an insurer to pursue any course of recovery of damages, in its name or in the name of the policyholder, against a third party who is liable for costs relating to an insured event that have been paid by the insurer. Estimated salvage and subrogation is generally deducted from the liability for unpaid claims. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 30 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479224/944-40-30-3 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 30 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479224/944-40-30-2 + Details
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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. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 7 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480046/944-40-55-7 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480081/944-40-50-3 + Details
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