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Reserves For Losses And Loss Expenses (Schedule of Liability for Unpaid Claims and Claims Adjustment Expense) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] |  |  |
Net reserves at beginning of year | $ 15,661,820 | $ 14,248,879 | $ 12,848,362
Net provision for losses and loss expenses: |  |  |
Claims occuring during the current year | 7,083,999 | 6,311,780 | 5,774,713
Increase in estimates for claims occurring in prior years (2) | 14,350 | 29,681 | 54,511
Loss reserve discount accretion | 33,246 | 30,681 | 32,526
Total | 7,131,595 | 6,372,142 | 5,861,750
Net payments for claims: |  |  |
Current year | 1,278,585 | 1,217,078 | 1,068,577
Prior year | 4,205,845 | 3,764,532 | 3,279,333
Total | 5,484,430 | 4,981,610 | 4,347,910
Foreign currency translation | (142,344) | 22,409 | (113,323)
Net reserves at end of year | 17,166,641 | 15,661,820 | 14,248,879
Ceded reserve at end of year | 3,201,389 | 3,077,832 | 2,762,344
Gross reserves at end of year | 20,368,030 | 18,739,652 | 17,011,223
Increase in estimates for claims occurring in prior years (2) | (14,350) | (29,681) | (54,511)
Retrospective premium adjustments for claims occurring in prior years (3) | 18,782 | 10,782 | 18,106
Net premium and reserve development on prior years | 4,432 | (18,899) | (36,405)
Workers' compensation discount, amount | 49,000 | 47,000 | 35,000
Increase (decrease) in estimates for claims occurring in prior years, undiscounted basis | $ 13,000 | $ (13,000) | $ 16,000

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- Definition The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date. + 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/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 9E -Publisher FASB -URI https://asc.fasb.org/1943274/2147480046/944-40-55-9E Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (cc) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480081/944-40-50-3 Reference 4: 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)(13)(a)(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1 + Details
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- Definition Amount, after effects of reinsurance, of payments to settle claims incurred in the current 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 (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480081/944-40-50-3 + Details
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- Definition Liability as of the balance sheet date for amounts representing estimated cost of settling unpaid claims under the terms of the underlying insurance policies, less estimated reinsurance recoveries on such claims. This includes an estimate for claims which have been incurred but not reported. Claim adjustment expenses represent the costs estimated to be incurred in the settlement of unpaid claims. + References Reference 1: 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)(13)(a)(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (cc) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480081/944-40-50-3 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480081/944-40-50-3 + Details
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