Goodwill (Carrying Amount of Goodwill) (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | 12 Months Ended | |||
|---|---|---|---|---|---|---|
Sep. 30, 2024 |
Sep. 30, 2023 |
Sep. 30, 2024 |
Sep. 30, 2023 |
Dec. 31, 2023 |
Sep. 30, 2020 |
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| Goodwill [Line Items] | ||||||
| Goodwill, gross | $ 210,725 | $ 210,725 | ||||
| Accumulated impairment loss | (205,225) | (205,225) | ||||
| Goodwill [Roll Forward] | ||||||
| Goodwill | 5,500 | $ 49,610 | $ 49,610 | |||
| Impairment losses | 0 | $ (44,110) | 0 | (44,110) | (44,110) | |
| Goodwill | 5,500 | 5,500 | 5,500 | 5,500 | 5,500 | |
| Specialty P&C | ||||||
| Goodwill [Line Items] | ||||||
| Goodwill, gross | 161,115 | 161,115 | ||||
| Accumulated impairment loss | (161,115) | (161,115) | $ (161,100) | |||
| Goodwill [Roll Forward] | ||||||
| Goodwill | 0 | 0 | ||||
| Impairment losses | 0 | 0 | ||||
| Goodwill | 0 | 0 | 0 | 0 | ||
| Workers' Compensation Insurance | ||||||
| Goodwill [Line Items] | ||||||
| Goodwill, gross | 44,110 | 44,110 | ||||
| Accumulated impairment loss | (44,110) | (44,100) | (44,110) | (44,100) | ||
| Goodwill [Roll Forward] | ||||||
| Goodwill | 44,110 | 44,110 | ||||
| Impairment losses | (44,100) | 0 | (44,110) | |||
| Goodwill | 0 | 0 | 0 | 0 | ||
| Segregated Portfolio Cell Reinsurance | ||||||
| Goodwill [Line Items] | ||||||
| Goodwill, gross | 5,500 | 5,500 | ||||
| Accumulated impairment loss | 0 | 0 | ||||
| Goodwill [Roll Forward] | ||||||
| Goodwill | 5,500 | 5,500 | ||||
| Impairment losses | 0 | $ 0 | ||||
| Goodwill | $ 5,500 | $ 5,500 | $ 5,500 | $ 5,500 | ||
| X | ||||||||||
- Definition Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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| X | ||||||||||
- Definition Amount, before accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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| X | ||||||||||
- Definition Amount of accumulated impairment loss for asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of impairment loss from asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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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. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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| X | ||||||||||
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. No definition available.
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