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Significant Transactions - WM Outrigger Re (Details) - USD ($) $ in Millions |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Dec. 20, 2022 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2024
Outrigger Re |  |  |  |  |
Other Significant Transactions [Line Items] |  |  |  |  |
Ceded unearned premiums |  | $ 230.0 | $ 250.0 |  | $ 230.0
Rollover amount |  | 130.0 | 130.0 |  |
Net distributions |  |  | 75.0 |  | 122.7
Commitment amount |  | 150.0 |  |  |
Short-term investments, at fair value |  | $ 203.7 | $ 265.3 |  | $ 203.7
Outrigger Re |  |  |  |  |
Other Significant Transactions [Line Items] |  |  |  |  |
Business combination, consideration transferred |  |  |  | $ 205.0 |
Redeemable Preferred Stock | Outrigger Re Ltd |  |  |  |  |
Other Significant Transactions [Line Items] |  |  |  |  |
Issuances of common shares | $ 250.0 |  |  |  |

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