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Income Taxes - Tax Effects of Deferred Tax Assets and Deferred Tax Liabilities (Details) - USD ($) $ in Millions | Dec. 31, 2017 | Dec. 31, 2016
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Income Tax Disclosure [Abstract] |  |
Share-based payments | $ 4.0 | $ 5.6
Operating loss carryforwards | 102.5 | 124.5
Loss reserves | 4.3 | 7.8
Accrued expenses | 7.9 | 14.4
Foreign tax credit carryforwards | 4.0 | 2.5
Unearned premiums | 11.8 | 20.0
Deferred policy acquisition costs | 5.9 | 2.1
Office properties and equipment | 8.0 | 5.6
Other temporary differences | 2.9 | 3.8
Total gross deferred tax assets | 151.3 | 186.3
Less valuation allowance | (104.8) | (142.5)
Net deferred tax assets | 46.5 | 43.8
Equalization provision reserves | 0.0 | (23.0)
Intangible assets (other) | (2.0) | (2.8)
Deferred policy acquisition costs | (14.5) | (22.4)
Other temporary differences | (1.7) | (1.7)
Total gross deferred tax (liabilities) | (18.2) | (49.9)
Deferred Tax Assets, Net | 28.3 |
Deferred tax liability | $ 0.0 | $ (6.1)

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