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Significant Transactions - Outrigger Re (Details) $ in Millions |  | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Dec. 20, 2022 USD ($) account | Jan. 31, 2024 USD ($) | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) | Dec. 31, 2023 USD ($)
Outrigger Re |  |  |  |  |
Other Significant Transactions [Line Items] |  |  |  |  |
Ceded unearned premiums |  |  | $ 250.0 |  | $ 250.0
Rollover amount |  |  | 130.0 |  |
Short-term investments |  |  | $ 265.3 | $ 203.7 | 265.3
Outrigger Re | Subsequent Event |  |  |  |  |
Other Significant Transactions [Line Items] |  |  |  |  |
Return of capital |  | $ 68.1 |  |  |
Outrigger Re |  |  |  |  |
Other Significant Transactions [Line Items] |  |  |  |  |
Business combination, consideration transferred |  |  |  | $ 205.0 |
Transaction costs |  |  |  |  | $ 1.3
Subsidiary - WM Outrigger Re | Preferred stocks |  |  |  |  |
Other Significant Transactions [Line Items] |  |  |  |  |
Basic ownership |  |  | 100.00% | 100.00% | 100.00%
Redeemable Preferred Stock | Outrigger Re Ltd |  |  |  |  |
Other Significant Transactions [Line Items] |  |  |  |  |
Issuances of common shares | $ 250.0 |  |  |  |
Number of segregated accounts | account | 4 |  |  |  |

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