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Basis of Presentation and Significant Accounting Policies (Details) $ in Millions | 12 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Dec. 31, 2023 USD ($) segment | Oct. 25, 2023 USD ($) | Dec. 31, 2022 USD ($) | Dec. 20, 2022 account | May 26, 2022 | May 25, 2022
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Number of reportable segments | segment | 3 |  |  |  |  |
Other long-term investments | $ 1,998.2 |  | $ 1,488.0 |  |  |
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List] | Other assets |  | Other assets |  |  |
Operating lease, right-of-use asset | $ 20.3 |  | $ 25.2 |  |  |
Operating Lease, Liability, Statement of Financial Position [Extensible List] | Other liabilities |  | Other liabilities |  |  |
Lease liabilities | $ 22.0 |  | $ 27.1 |  |  |
Net unrealized foreign currency translation gain (losses) | $ (1.6) |  | (3.5) |  |  |
Third Point Re | Ark |  |  |  |  |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Annual crediting rate | 3.00% |  |  |  |  |
Level 2 |  |  |  |  |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Variance threshold for outliers | $ 0.5 |  |  |  |  |
Variance threshold for outliers (as a percent) | 5.00% |  |  |  |  |
Level 2 | Fair value measured on a recurring basis | Other long-term investments |  |  |  |  |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Other long-term investments | $ 26.2 |  | 14.8 |  |  |
Level 3 | Fair value measured on a recurring basis | Other long-term investments |  |  |  |  |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Other long-term investments | 1,138.2 |  | 911.6 |  |  |
NAV | Fair value measured on a recurring basis | Other long-term investments |  |  |  |  |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Other long-term investments | $ 833.8 |  | $ 561.6 |  |  |
Redeemable Preferred Stock | Outrigger Re Ltd |  |  |  |  |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Number of segregated accounts | account |  |  |  | 4 |  |
Ark |  |  |  |  |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Percent of shares outstanding | 12.50% |  |  |  |  |
Subsidiary - HG Global | Preferred stocks |  |  |  |  |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Basic ownership | 96.90% |  | 96.90% |  |  |
Subsidiary - HG Global | Common Stock |  |  |  |  |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Basic ownership | 88.40% |  | 88.40% |  |  |
Subsidiary - Ark Insurance Holdings Limited |  |  |  |  |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Basic ownership | 72.00% |  | 72.00% |  |  |
Ownership percentage, after equity incentives | 61.90% |  | 63.00% |  |  |
Subsidiary - WM Outrigger Re | Preferred stocks |  |  |  |  |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Basic ownership | 100.00% |  | 100.00% |  |  |
Subsidiary - Kudu Investment Management, LLC |  |  |  |  |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Basic ownership |  |  | 89.60% |  |  |
Ownership percentage basic units outstanding |  |  | 89.30% |  | 89.30% | 99.10%
Ownership percentage, fully diluted | 76.30% |  |  |  |  |
Ownership percentage, fully converted |  |  | 76.10% |  |  |
Subsidiary - HG Global |  |  |  |  |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Purchase of surplus notes | $ 503.0 |  |  |  |  |
Subsidiary - HG Global | Maximum |  |  |  |  |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Percentage of par value of policy reinsured | 15.00% |  |  |  |  |
Subsidiary - WTM Partners |  |  |  |  |  |
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items] |  |  |  |  |  |
Expected capital contribution |  | $ 500.0 |  |  |  |

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