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Segment Reporting Disclosures (Summary of Gross Premium Volume and Net Written Premiums) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Schedule of GWP and NWP, by Segment [Line Items] |  |  |
Gross written premiums | $ 15,494,631 | $ 14,002,237 | $ 13,201,682
Net written premiums | 8,296,175 | 8,397,575 | 8,203,390
Underwriting Operations [Member] |  |  |
Schedule of GWP and NWP, by Segment [Line Items] |  |  |
Gross written premiums | 10,551,873 | 10,277,632 | 9,847,538
Net written premiums | 8,299,751 | 8,398,788 | 8,207,373
Insurance [Member] |  |  |
Schedule of GWP and NWP, by Segment [Line Items] |  |  |
Gross written premiums | 9,400,316 | 9,217,150 | 8,606,700
Net written premiums | 7,260,089 | 7,432,062 | 7,040,176
Reinsurance [Member] |  |  |
Schedule of GWP and NWP, by Segment [Line Items] |  |  |
Gross written premiums | 1,150,780 | 1,046,539 | 1,229,851
Net written premiums | 1,039,372 | 967,799 | 1,167,312
Other underwriting [Member] |  |  |
Schedule of GWP and NWP, by Segment [Line Items] |  |  |
Gross written premiums | 777 | 13,943 | 10,987
Net written premiums | 290 | (1,073) | (115)
Fronting [Member] |  |  |
Schedule of GWP and NWP, by Segment [Line Items] |  |  |
Gross written premiums | 4,942,758 | 3,724,605 | 3,354,144
Net written premiums | $ (3,576) | $ (1,213) | $ (3,983)

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- Definition Amount of direct and assumed premiums written. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 1 -SubTopic 605 -Topic 944 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479032/944-605-50-1 + Details
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- Definition Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums written. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c)(1) -SubTopic 605 -Topic 944 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479032/944-605-50-1 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(1) -SubTopic 605 -Topic 944 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479032/944-605-50-1 + Details
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