Reinsurance Reinsurance (Effect Of Reinsurance And Retrocessional Reinsurance On Losses) (Details) - Underwriting [Member] - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Effects of Reinsurance [Line Items]
Gross losses and loss adjustment expenses	$ 1,392,348	$ 1,150,349
Ceded losses and loss adjustment expenses	(219,255)	(177,994)
Net losses and loss adjustment expenses	$ 1,173,093	$ 972,355

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Amount, before effect of policies assumed or ceded, of expense related to provision for policy benefits and costs incurred.

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Amount, after effects of policies assumed or ceded, of expense related to the provision for policy benefits and costs incurred.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
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Amount of reduction of provision for policy benefits and costs incurred for policies ceded.

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