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Related Party Transactions (Narrative) (Details) - USD ($) $ in Thousands |  | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | ---
Jun. 01, 2023 | Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022 | Dec. 31, 2022
Related Party Transaction [Line Items] |  |  |  |  |  |
Services and other revenues |  | $ 725,627 | $ 691,653 | $ 1,963,779 | $ 1,962,585 |
Reinsurance recoverables |  | 8,534,919 |  | 8,534,919 |  | $ 8,446,745
ISIC [Member] |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |
Gain on sale of business | $ 16,900 |  |  |  |  |
Nephila Reinsurers [Member] |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |
Reinsurance recoverables |  | 874,100 |  | 874,100 |  | 1,400,000
Hagerty, Inc. [Member] |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |
Reinsurance recoverables |  | 200,000 |  | 200,000 |  | $ 159,700
Insurance-linked Securities Operations [Member] | Unconsolidated entities managed by Nephila [Member] |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |
Services and other revenues |  | $ 43,600 | $ 17,100 | $ 74,100 | $ 57,000 |

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- Definition Amount, after valuation allowance, recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, policy benefits and policy reserves. Excludes premiums paid under reinsurance contracts. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 310 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479584/944-310-50-2 Reference 2: 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 3: 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 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 310 -Name Accounting Standards Codification -Section 45 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479616/944-310-45-6 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 825 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479383/944-825-50-1B + Details
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