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Reserves For Losses And Loss Expenses (Narrative) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Reserves For Losses And Loss Expenses [Line Items] |  |  |
Liability recognized for best estimate net of reinsurance | $ 384,000 |  |
Liability recognized for best estimate net of reinsurance, incurred but not reported (IBNR) | 3,000 |  |
Favorable reserve development net of premium offsets | (18,899) | $ (36,405) | $ 6,647
Reserve for losses and loss adjustment expenses relating to asbestos and environmental claims, net | 17,000 | 20,000 |
Workers' Compensation Discount, Prior Year Amount | 1,352,000 | 1,464,000 |
Workers' compensation discount after effects of ceded reinsurance, amount | 390,000 | 416,000 |
Liability recognized for best estimate net of reinsurance, reported losses | 381,000 |  |
Liability recognized for best estimate net of reinsurance, current accident year losses | $ 1,000 |  |
Minimum |  |  |
Reserves For Losses And Loss Expenses [Line Items] |  |  |
Workers' compensation discount, percent | 0.70% |  |
Maximum |  |  |
Reserves For Losses And Loss Expenses [Line Items] |  |  |
Workers' compensation discount, percent | 6.50% |  |
Weighted Average |  |  |
Reserves For Losses And Loss Expenses [Line Items] |  |  |
Workers' compensation discount, percent | 3.50% |  |
Discounted [Member] |  |  |
Reserves For Losses And Loss Expenses [Line Items] |  |  |
Workers' compensation discount, percent | 3.00% |  |
Insurance |  |  |
Reserves For Losses And Loss Expenses [Line Items] |  |  |
Liability recognized for best estimate net of reinsurance | $ 326,000 |  |
Favorable reserve development net of premium offsets |  |  | 20,000
Unfavorable reserve development net of premium offsets | 24,000 | 40,000 |
Reinsurance & Monoline Excess |  |  |
Reserves For Losses And Loss Expenses [Line Items] |  |  |
Liability recognized for best estimate net of reinsurance | 58,000 |  |
Favorable reserve development net of premium offsets |  | $ 4,000 |
Unfavorable reserve development net of premium offsets | $ 5,000 |  | $ 13,000
Excess workers' compensation |  |  |
Reserves For Losses And Loss Expenses [Line Items] |  |  |
Workers' compensation discount, percent | 97.00% |  |

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- Definition Carrying amount as of the balance sheet date of reserves for the costs of settling insured claims and costs incurred in the claims settlement process attributable to asbestos and environmental claims, net of estimated reinsurance recoveries. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -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 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-3 + Details
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- Definition Percent discount applied to worker's compensation reserve liability to reduce the reserve to present value. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-6 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-1 + Details
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- Definition Prior year monetary amount of the change in worker's compensation reserve liability resulting from the discount applied to reduce the reserve to present value. + References No definition available. + Details
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- Definition Liability for Claims and Claims Adjustment Expense, Net Of Reinsurance, Current Accident Year Losses + References No definition available. + Details
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- Definition Liability for Claims and Claims Adjustment Expense, Net Of Reinsurance, Incurred but Not Reported (IBNR) Claims, Amount + References No definition available. + Details
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- Definition Reserves For Losses And Loss Expenses [Line Items] + References No definition available. + Details
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