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Income Taxes (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2025 | Mar. 31, 2024 | Dec. 31, 2023
Investments, Owned, Federal Income Tax Note [Line Items] |  |  |
Net deferred tax benefit | $ 73.0 |  | $ 68.0
Effective tax rate | 13.30% | 4.60% |
P&C Insurance and Reinsurance (Ark/WM Outrigger) | Ark |  |  |
Investments, Owned, Federal Income Tax Note [Line Items] |  |  |
Net deferred tax benefit | $ 51.0 |  | 51.0
Financial Guarantee (HG Global) | HG Global |  |  |
Investments, Owned, Federal Income Tax Note [Line Items] |  |  |
Net deferred tax benefit | 22.0 |  | $ 17.0
Deferred tax liabilities | $ 5.0 |  |

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