Business Segments - Segment Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) segment	Jun. 30, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of Operating Segments | segment			2
Earned Premiums	$ 553.7	$ 500.1	$ 1,099.7	$ 931.4
Net Investment Income	73.7	76.7	140.7	147.3
Other Income	0.6	0.6	1.4	1.5
Total Revenues	627.2	609.2	1,238.5	1,108.4
Net Realized Gains on Sales of Investments	5.6	34.0	12.4	37.4
Segment Operating Profit (Loss)	3.4	2.5	(0.6)	33.0
Net Impairment Losses Recognized in Earnings	(6.4)	(2.2)	(15.7)	(9.2)
Loss from Early Extinguishment of Debt	0.0	0.0	0.0	9.1
Total Before Income Taxes	2.6	34.3	(3.9)	52.1
Segment Net Operating Income (Loss)	4.6	6.7	4.0	28.5
Income (Loss) from Continuing Operations Attributable to Parent	4.1	27.4	1.9	40.9
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Segment Operating Profit (Loss)	(4.7)	(11.3)	(16.9)	(23.6)
Segment Net Operating Income (Loss)	(2.9)	(5.0)	(10.7)	(12.7)
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Other Income	3.8	4.9	3.9	10.1
Net Realized Gains on Sales of Investments	5.6	34.0	12.4	37.4
Net Impairment Losses Recognized in Earnings	(6.4)	(2.2)	(15.7)	(9.2)
Loss from Early Extinguishment of Debt	0.0	0.0	0.0	(9.1)
Net Realized Gains (Losses) on Sales of Investments, Net of Tax	3.7	22.1	8.1	24.3
Net Impairment Losses Recognized in Earnings, Net of Tax	(4.2)	(1.4)	(10.2)	(6.0)
Loss from Early Extinguishment of Debt, Net of Tax	0.0	0.0	0.0	(5.9)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	624.2	572.5	1,237.9	1,070.1
Segment Operating Profit (Loss)	8.1	13.8	16.3	56.6
Income (Loss) from Continuing Operations Attributable to Parent	7.5	11.7	14.7	41.2
Operating Segments [Member] | Property and Casualty Insurance [Member]
Segment Reporting Information [Line Items]
Earned Premiums	402.6	349.4	798.8	637.0
Net Investment Income	19.7	18.6	31.6	33.4
Other Income	0.1	0.1	0.3	0.4
Total Revenues	422.4	368.1	830.7	670.8
Segment Operating Profit (Loss)	(17.2)	(8.4)	(40.0)	9.6
Income (Loss) from Continuing Operations Attributable to Parent	(8.9)	(2.6)	(22.0)	10.8
Operating Segments [Member] | Life and Health Insurance [Member]
Segment Reporting Information [Line Items]
Earned Premiums	151.1	150.7	300.9	294.4
Net Investment Income	50.1	53.5	105.1	103.9
Other Income	0.6	0.2	1.2	1.0
Total Revenues	201.8	204.4	407.2	399.3
Segment Operating Profit (Loss)	25.3	22.2	56.3	47.0
Income (Loss) from Continuing Operations Attributable to Parent	$ 16.4	$ 14.3	$ 36.7	$ 30.4