Unpaid Losses And Loss Adjustment Expenses (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
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

Catastrophe Current Year Claims and Claims Adjustment Expense

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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.

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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
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-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
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