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LOSS AND LOSS ADJUSTMENT EXPENSE RESERVES - Narrative (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2025 | Mar. 31, 2024 | Dec. 31, 2024 | Dec. 31, 2023
Liability for Claims and Claims Adjustment Expense |  |  |  |
CAT losses | $ 27,015 | $ 12,437 |  |
Prior years | 4,218 | 5,401 | $ 4,218 | $ 5,401
California Wildfires |  |  |  |
Liability for Claims and Claims Adjustment Expense |  |  |  |
CAT losses | 27,000 |  |  |
Baltimore Bridge Collapse |  |  |  |
Liability for Claims and Claims Adjustment Expense |  |  |  |
CAT losses |  | 12,400 |  |
Operating Segments |  |  |  |
Liability for Claims and Claims Adjustment Expense |  |  |  |
Prior years | 4,329 | 1,472 |  |
Operating Segments | Open Market |  |  |  |
Liability for Claims and Claims Adjustment Expense |  |  |  |
CAT losses | 27,015 | 12,437 |  |
Prior years | 4,896 | 1,473 | 4,896 | 1,473
Operating Segments | Innovations |  |  |  |
Liability for Claims and Claims Adjustment Expense |  |  |  |
CAT losses | 0 | 0 |  |
Prior years | (567) | (1) | $ (567) | $ (1)
Operating Segments | Reinsurance Contract [Axis]: Adverse Reserve Development | Open Market |  |  |  |
Liability for Claims and Claims Adjustment Expense |  |  |  |
Prior years | 23,200 | 4,100 |  |
Operating Segments | Reinsurance Contract [Axis]: Favorable Reserve Development | Open Market |  |  |  |
Liability for Claims and Claims Adjustment Expense |  |  |  |
Prior years | $ (18,300) | $ (2,700) |  |

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