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Reinsurance (Schedule Of Ceded Credit Risk by Reinsurer) (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Ceded Credit Risk [Line Items]
Uncollectible reinsurance	$ (8,350)	$ (8,404)	$ (8,064)
Ceded reserve at end of year	3,557,695
Credit Risk Reinsurers, Subtotal, Excluding Residual Market Pools
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	3,445,123
Lifson Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	416,509
Lloyds of London
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	356,338
Partner Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	314,891
Munich Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	287,864
Berkshire Hathaway
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	274,182
Hannover Re Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	222,719
Renaissance Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	215,300
Swiss Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	159,462
Liberty Mutual
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	120,381
Everest Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	93,223
Axis Capital
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	83,756
Arch Capital Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	67,357
Sompo Holdings Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	59,074
Fairfax Financial
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	58,585
Nationwide Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	52,111
Korean Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	51,233
Axa Insurance
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	50,002
TOA Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	47,501
Markel Corp Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	42,982
MS & AD Insurance Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	34,680
Helvetia Holdings Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	29,490
Chubb Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	26,708
Other Reinsurers Less than $20,000
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	380,775
Residual Market Pools
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	$ 120,922

X

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 825
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477351/944-825-50-1B

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Amount, after valuation allowance, recoverable under reinsurance contracts including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479838/944-20-50-5

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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-Topic 944
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-Section S99
-Paragraph 1
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Amount of allowance for credit loss on reinsurance recoverable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
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-URI https://asc.fasb.org/1943274/2147479838/944-20-50-5

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