Quarterly Financial Information (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues [Abstract]
Earned Premiums	$ 520.8	$ 527.3	$ 529.8	$ 529.2	$ 536.5	$ 543.0	$ 548.1	$ 546.0	$ 2,107.1	$ 2,173.6	$ 2,289.4
Net Investment Income	72.9	70.4	75.2	77.4	75.3	58.6	82.9	81.2	295.9	298.0	325.7
Other Income	0.2	0.2	0.2	0.2	0.2	0.4	0.2	0.2	0.8	1.0	1.3
Net Realized Gains (Losses) on Sales of Investments	5.5	50.9	4.1	4.9	5.9	(4.2)	17.8	14.2	65.4	33.7	42.6
Other-than-temporary Impairment Losses:
Total Other-than-temporary Impairment Losses	(3.1)	(3.2)	(0.4)	(0.5)	(4.7)	(5.0)	(1.3)	(0.4)	(7.2)	(11.4)	(17.7)
Portion of Losses Recognized in Other Comprehensive Income	0.3	0	0	0	0.1	0	0	0	0.3	0.1	1.2
Net Impairment Losses Recognized in Earnings	2.8	3.2	0.4	0.5	4.6	5.0	1.3	0.4	6.9	11.3	16.5
Total Revenues	596.6	645.6	608.9	611.2	613.3	592.8	647.7	641.2	2,462.3	2,495.0	2,642.5
Expenses [Abstract]
Policyholders' Benefits and Incurred Losses and Loss Adjustment Expenses	413.0	368.7	423.8	376.6	376.7	399.6	477.1	392.3	1,582.1	1,645.7	1,647.2
Insurance Expenses	169.5	172.7	167.7	162.4	170.1	176.8	170.6	166.1	672.3	683.6	685.9
Write-off of Goodwill and Other Intangibles Acquired					13.5	0	0	0	0	13.5	14.8
Interest and Other Expenses	20.1	22.7	20.9	21.8	21.9	21.4	20.9	19.7	85.5	83.9	68.3
Total Expenses	602.6	564.1	612.4	560.8	582.2	597.8	668.6	578.1	2,339.9	2,426.7	2,416.2
Income from Continuing Operations before Income Taxes and Equity in Net Loss of Former Investee	(6.0)	81.5	(3.5)	50.4	31.1	(5.0)	(20.9)	63.1	122.4	68.3	226.3
Income Tax Benefit (Expense)	4.3	(25.9)	5.1	(14.1)	(6.1)	6.1	11.5	(18.1)	(30.6)	(6.6)	(63.8)
Income from Continuing Operations	(1.7)	55.6	1.6	36.3	25.0	1.1	(9.4)	45.0	91.8	61.7	162.4
Income from Discontinued Operations before Income Taxes	5.7	(0.1)	1.0	12.3	0.2	0.6	9.3	9.4	18.9	19.5	25.8
Income Tax Benefit (Expense)	(2.1)	0.1	(0.3)	(5.0)	(0.9)	0.3	(3.2)	(2.9)	(7.3)	(6.7)	(10.3)
Income from Discontinued Operations	3.6	0	0.7	7.3	(0.7)	0.9	6.1	6.5	11.6	12.8	15.5
Net Income	$ 1.9	$ 55.6	$ 2.3	$ 43.6	$ 24.3	$ 2.0	$ (3.3)	$ 51.5	$ 103.4	$ 74.5	$ 177.9
Income (Loss) from Continuing Operations Per Unrestricted Share [Abstract]
Income from Continuing Operations Per Unrestricted Share - Basic	$ (0.03)	$ 0.95	$ 0.03	$ 0.61	$ 0.41	$ 0.01	$ (0.16)	$ 0.74	$ 1.55	$ 1.02	$ 2.62
Income from Continuing Operations Per Unrestricted Share - Diluted	$ (0.03)	$ 0.95	$ 0.03	$ 0.60	$ 0.41	$ 0.01	$ (0.16)	$ 0.73	$ 1.54	$ 1.02	$ 2.62
Net Income (Loss) Per Unrestricted Share [Abstract]
Net Income Per Unrestricted Share - Basic	$ 0.03	$ 0.95	$ 0.04	$ 0.73	$ 0.40	$ 0.03	$ (0.06)	$ 0.85	$ 1.75	$ 1.23	$ 2.87
Net Income Per Unrestricted Share - Diluted	$ 0.03	$ 0.95	$ 0.04	$ 0.72	$ 0.40	$ 0.03	$ (0.06)	$ 0.84	$ 1.74	$ 1.23	$ 2.87
Dividends Paid to Shareholders Per Share	$ 0.24	$ 0.24	$ 0.24	$ 0.24	$ 0.24	$ 0.24	$ 0.24	$ 0.24	$ 0.96	$ 0.96	$ 0.88