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Reinsurance (Schedule Of Ceded Credit Risk by Reinsurer) (Details) - USD ($) $ in Thousands | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
--- | --- | --- | ---
Ceded Credit Risk [Line Items] |  |  |
Uncollectible reinsurance | $ (8,404) | $ (8,064) | $ (7,713)
Ceded reserve at end of year | 3,534,527 |  |
Credit Risk Reinsurers, Subtotal, Excluding Residual Market Pools [Member] |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 3,408,138 |  |
Lloyds of London |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 402,210 |  |
Lifson Re |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 335,382 |  |
Partner Re |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 314,471 |  |
Munich Re |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 310,985 |  |
Berkshire Hathaway |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 307,878 |  |
Hannover Re Group |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 231,172 |  |
Renaissance Re |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 217,008 |  |
Swiss Re |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 176,377 |  |
Everest Re |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 145,155 |  |
Liberty Mutual |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 117,556 |  |
Axis Capital |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 86,680 |  |
Fairfax Financial |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 64,300 |  |
Korean Re |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 57,530 |  |
Arch Capital Group |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 54,175 |  |
Sompo Holdings Group |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 47,520 |  |
Axa Insurance |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 45,680 |  |
TOA Re |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 37,140 |  |
Nationwide Group |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 32,411 |  |
Markel Corp Group |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 31,827 |  |
Helvetia Holdings Group |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 31,429 |  |
Chubb Group |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 24,459 |  |
MS & AD Insurance Group |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 20,144 |  |
Other Reinsurers Less than $20,000 |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | 316,649 |  |
Residual Market Pools |  |  |
Ceded Credit Risk [Line Items] |  |  |
Ceded reserve at end of year | $ 134,793 |  |

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- Definition 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 -Topic 944 -SubTopic 310 -Name Accounting Standards Codification -Section 45 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479616/944-310-45-5 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(6)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1 + Details
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