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Income Taxes - Tax Effects of Deferred Tax Assets and Deferred Tax Liabilities (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022
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Income Tax Disclosure [Abstract] |  |
Operating loss carryforwards | $ 217.2 | $ 167.6
Capital loss carryforwards | 9.7 | 6.7
Insurance reserves: Losses and loss adjustment expenses | 104.1 | 28.3
Unrealized losses on investments | 8.9 | 20.6
Accrued expenses | 13.4 | 6.1
Foreign tax credit carryforwards | 19.0 | 19.8
Unearned premiums | 35.0 | 36.0
Intangible assets | 82.9 | 0.7
Office properties and equipment | 16.5 | 14.2
Operating lease liability | 15.6 | 18.5
Other temporary differences | 7.6 | 3.7
Total deferred tax assets | 529.9 | 322.2
Less valuation allowance | (172.7) | (145.7)
Deferred tax assets, net of valuation allowance | 357.2 | 176.5
Deferred acquisition costs | (32.4) | (37.0)
Operating lease assets | (10.4) | (13.7)
Deferred Tax Liabilities, GAAP differences | 0.1 | 0.2
Other temporary differences | (3.3) | (6.4)
Total deferred tax (liabilities) | (46.2) | (57.3)
Deferred tax assets, net | $ 311.0 | $ 119.2

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