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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, 2022 | Dec. 31, 2021 | Dec. 31, 2020
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Abstract] |  |  |
Deferred policy acquisition costs | $ 763,486 | $ 676,145 | $ 556,168
Reserves for losses and loss expenses | 17,011,223 | 15,390,888 | 13,784,430
Unearned premiums | 5,297,654 | 4,847,160 | 4,073,191
Net premiums earned | 9,561,429 | 8,106,031 | 6,930,843
Net investment income | 779,185 | 671,618 | 583,821
Losses and loss expenses incurred: |  |  |
Current year | 5,774,713 | 4,921,191 | 4,432,937
Prior years | 54,511 | 863 | 627
Loss reserve discount accretion | 32,526 | 31,906 | 35,142
Amortization of deferred policy acquisition costs |  | 961,628 | 904,955
Paid losses and loss expenses | 4,347,910 | 3,665,694 | 3,598,649
Net premiums written | $ 10,004,070 | $ 8,862,867 | $ 7,262,437

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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 -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-18(Column I)) -URI http://asc.fasb.org/extlink&oid=120401096&loc=d3e575016-122915 + 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/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=116884095&loc=d3e14764-158437 + Details
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- Definition Amount of premium revenue earned by property-casualty insurance underwriter. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-18(Column F)) -URI http://asc.fasb.org/extlink&oid=120401096&loc=d3e575016-122915 + Details
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- Definition Amount of loss reported and paid for claim and claim adjustment expense by property-casualty insurance underwriter. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-18(Column J)) -URI http://asc.fasb.org/extlink&oid=120401096&loc=d3e575016-122915 + Details
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