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Unpaid Losses And Loss Adjustment Expenses (Narrative) (Details) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2025 | Mar. 31, 2024
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Catastrophe Current Year Claims and Claims Adjustment Expense | $ 66,063 | $ 0
Favorable (adverse) development on prior years' loss reserves | 150,107 | 77,023
California Wildfires (2025) |  |
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Catastrophe Current Year Claims and Claims Adjustment Expense | 66,100 |
Insurance [Member] |  |
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Catastrophe Current Year Claims and Claims Adjustment Expense | 64,113 | 0
Insurance [Member] | International professional liability and marine and energy product lines |  |
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Favorable (adverse) development on prior years' loss reserves |  | $ 64,800
Insurance and Reinsurance | Professional liability and general liability product lines |  |
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Favorable (adverse) development on prior years' loss reserves | $ 109,200 |

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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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