Business Segments - Segment Information (Details) - Segment [Domain] $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) segments	Jun. 30, 2014 USD ($)
Segment Reporting Information [Line Items]
Number of Operating Segments | segments			2
Earned Premiums	$ 500.1	$ 470.3	$ 931.4	$ 947.9
Net Investment Income	76.7	72.6	147.3	143.7
Other Income	0.6	0.2	1.5	0.3
Total Revenues	609.2	542.5	1,108.4	1,097.1
Net Realized Gains on Sales of Investments	34.0	3.5	37.4	10.1
Segment Operating Profit (Loss)	2.5	11.8	33.0	57.9
Net Impairment Losses Recognized in Earnings	(2.2)	(4.1)	(9.2)	(4.9)
Loss from Early Extinguishment of Debt	0.0	0.0	9.1	0.0
Income from Continuing Operations before Income Taxes	34.3	11.2	52.1	63.1
Segment Net Operating Income (Loss)	6.7	9.6	28.5	41.1
Extinguishment of Debt, Gain (Loss), Net of Tax	0.0	0.0
Income from Continuing Operations	27.4	9.3	40.9	44.5
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Segment Operating Profit (Loss)	(11.3)	(8.6)	(23.6)	(16.4)
Segment Net Operating Income (Loss)	(5.0)	(5.1)	(12.7)	(10.1)
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Other Income	4.9	5.1	10.1	8.4
Net Realized Gains on Sales of Investments	34.0	3.5	37.4	10.1
Net Impairment Losses Recognized in Earnings	(2.2)	(4.1)	(9.2)	(4.9)
Loss from Early Extinguishment of Debt	0.0	0.0	(9.1)	0.0
Net Realized Gains (Losses) on Sales of Investments, Net of Tax	22.1	2.4	24.3	6.6
Net Impairment Losses Recognized in Earnings, Net of Tax	(1.4)	(2.7)	(6.0)	(3.2)
Extinguishment of Debt, Gain (Loss), Net of Tax			(5.9)	0.0
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	572.5	538.0	1,070.1	1,083.5
Segment Operating Profit (Loss)	13.8	20.4	56.6	74.3
Segment Net Operating Income (Loss)	$ 11.7	$ 14.7	$ 41.2	$ 51.2