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Significant Transactions - Outrigger Re (Details) - USD ($) |  | 3 Months Ended
--- | --- | ---
Dec. 20, 2022 | Mar. 31, 2025 | Dec. 31, 2024 | Mar. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Redeemable Preferred Stock | Outrigger Re Ltd |  |  |  |  |  |
Other Significant Transactions [Line Items] |  |  |  |  |  |
Issuances of common shares | $ 250,000,000 |  |  |  |  |
Outrigger Re |  |  |  |  |  |
Other Significant Transactions [Line Items] |  |  |  |  |  |
Business Combination, Consideration Transferred |  |  |  |  |  | $ 205,000,000
Outrigger Re |  |  |  |  |  |
Other Significant Transactions [Line Items] |  |  |  |  |  |
Ceded unearned premiums |  |  | $ 230,000,000 |  | $ 250,000,000 |
Rollover amount |  |  | 130,000,000 |  | 130,000,000 |
Return of capital |  | $ 0 |  | $ 68,100,000 | $ 75,000,000 |
Prepaid Reinsurance Premium, Commitment Amount |  |  | 150,000,000 |  |  |
Short-term investments, at fair value |  | $ 208,700,000 | $ 203,700,000 |  |  |

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