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LOSS AND LOSS ADJUSTMENT EXPENSE RESERVES - Narrative (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Liability for Claims and Claims Adjustment Expense |  |  |  |
CAT event losses | $ 0 | $ 12,147 | $ 27,016 | $ 29,869
Prior years | 817 | (5,655) | 8,082 | (943)
Operating Segments |  |  |  |
Liability for Claims and Claims Adjustment Expense |  |  |  |
Prior years |  |  | 6,126 | (5,330)
Operating Segments | Open Market |  |  |  |
Liability for Claims and Claims Adjustment Expense |  |  |  |
CAT event losses | 0 | 7,500 | 27,016 | 17,500
Prior years | 855 | (5,315) | 4,810 | (3,782)
Operating Segments | Innovations |  |  |  |
Liability for Claims and Claims Adjustment Expense |  |  |  |
CAT event losses | 0 | 0 | 0 | 0
Prior years | $ (648) | $ 94 | 1,316 | (1,548)
Operating Segments | Reinsurance Contract [Axis]: Adverse Reserve Development | Open Market |  |  |  |
Liability for Claims and Claims Adjustment Expense |  |  |  |
Prior years |  |  | 46,400 | 4,500
Operating Segments | Reinsurance Contract [Axis]: Adverse Reserve Development | Innovations |  |  |  |
Liability for Claims and Claims Adjustment Expense |  |  |  |
Prior years |  |  | 2,600 | (600)
Operating Segments | Reinsurance Contract [Axis]: Favorable Reserve Development | Open Market |  |  |  |
Liability for Claims and Claims Adjustment Expense |  |  |  |
Prior years |  |  | (41,600) | (8,300)
Operating Segments | Reinsurance Contract [Axis]: Favorable Reserve Development | Innovations |  |  |  |
Liability for Claims and Claims Adjustment Expense |  |  |  |
Prior years |  |  | $ (1,300) | $ 2,200

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