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Unpaid Losses And Loss Adjustment Expenses (Narrative) (Details) - USD ($) $ in Thousands | 6 Months Ended
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Jun. 30, 2024 | Jun. 30, 2023
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Favorable (adverse) development on prior years' loss reserves | $ 221,298 | $ 139,208
Reinsurance recoverable for retroactive reinsurance transaction | 0 | (125,067)
Insurance [Member] | International professional liability, marine and energy, credit and surety and general liability product lines [Member] |  |
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Favorable (adverse) development on prior years' loss reserves | $ 190,700 |
Insurance [Member] | Professional liability, property, marine and energy and workers' compensation product lines [Member] |  |
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Favorable (adverse) development on prior years' loss reserves |  | 169,600
Insurance [Member] | General liability product lines |  |
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Favorable (adverse) development on prior years' loss reserves |  | (53,000)
Reinsurance [Member] |  |
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Reinsurance recoverable for retroactive reinsurance transaction |  | (125,100)
Reinsurance [Member] | Professional liability and property product lines |  |
Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] |  |
Favorable (adverse) development on prior years' loss reserves |  | $ 20,900

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