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Schedule VI - Supplementary Information Concerning Property-Casualty Insurance Operations (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Abstract] |  |  |
Deferred policy acquisition costs | $ 951,728 | $ 861,609 | $ 763,486
Reserves for losses and loss expenses | 20,368,030 | 18,739,652 | 17,011,223
Unearned premiums | 6,375,112 | 5,922,326 | 5,297,654
Net premiums earned | 11,548,485 | 10,400,687 | 9,561,429
Net investment income | 1,333,161 | 1,052,835 | 779,185
Losses and loss expenses incurred: |  |  |
Current year | 7,083,999 | 6,311,780 | 5,774,713
Prior years | 14,350 | 29,681 | 54,511
Loss reserve discount accretion | 33,246 | 30,681 | 32,526
Amortization of deferred policy acquisition costs |  | 1,038,975 | 1,038,903
Paid losses and loss expenses | 5,484,430 | 4,981,610 | 4,347,910
Net premiums written | $ 11,972,096 | $ 10,954,467 | $ 10,004,070

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- Definition Amount of amortization expense on deferred policy acquisition cost for property-casualty insurance underwriter. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 235 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-18(Column I)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477965/944-235-S99-3 + Details
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- Definition Amount, after effects of reinsurance, of expense for claims incurred in the current reporting period and related claims settlement costs. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 7 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480046/944-40-55-7 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480081/944-40-50-3 + Details
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