Income Taxes - Schedule of Temporary Differences That Give Rise to Net Deferred Income Tax Assets (Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Deferred Income Tax Assets:
Insurance Reserves	$ 83.0	$ 78.7
Unearned Premium Reserves	41.7	35.5
Tax Capitalization of Policy Acquisition Costs	71.5	73.0
Payroll and Employee Benefit Accruals	72.0	74.0
Net Operating Loss Carryforward	30.5	31.7
Other	15.7	9.8
Total Deferred Income Tax Assets	314.4	302.7
Deferred Income Tax Liabilities:
Investments	109.8	160.1
Deferred Policy Acquisition Costs	110.7	106.1
Life VIF and P&C Customer Relationships	15.5	17.7
Goodwill and Other Intangible Assets Acquired	37.0	28.4
Depreciable Assets	7.3	7.4
Other	2.2	4.5
Total Deferred Income Tax Liabilities	282.5	324.2
Net Deferred Income Tax Liabilities	$ 31.9	$ (21.5)