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Reserve for Loss and Loss Expense (Insurance Subsidiaries) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Prior year development | $ (9,954) | $ (78,890) | $ (82,853)
Favorable or unfavorable loss development [Member] |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Prior year development | (10,000) | (78,900) | (82,900)
Favorable or unfavorable loss development [Member] | Casualty Insurance Product Line [Member] |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Prior year development | (6,500) | (86,000) | (81,000)
Favorable or unfavorable loss development [Member] | Property Insurance [Member] |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Prior year development | $ (16,500) | (7,100) | (1,900)
Favorable or unfavorable loss development [Member] | E&S Lines [Member] |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Prior year development |  |  | (7,000)
Favorable or unfavorable loss development [Member] | Commercial Automobile [Member] |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Prior year development |  | (22,500) | (13,300)
Favorable or unfavorable loss development [Member] | Commercial Automobile [Member] | Casualty Insurance Product Line [Member] |  |  |
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |
Prior year development |  | $ (15,000) | $ (15,000)

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Amount, after effects of reinsurance, of expense (reversal of expense) for claims incurred in prior reporting periods and related claims settlement costs. + References Reference 1: 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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