Consolidated Statements of Income (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues:
Earned Premiums	$ 536.5	$ 543.0	$ 548.1	$ 546.0	$ 561.6	$ 568.2	$ 578.1	$ 581.5	$ 2,173.6	$ 2,289.4	$ 2,455.5
Net Investment Income	75.3	58.6	82.9	81.2	84.7	79.4	81.3	80.3	298.0	325.7	319.9
Other Income	0.2	0.4	0.2	0.2	0.3	0.4	0.3	0.3	1.0	1.3	2.5
Net Realized Gains on Sales of Investments	5.9	(4.2)	17.8	14.2	28.0	7.2	2.9	4.5	33.7	42.6	24.6
Other-than-temporary Impairment Losses:
Total Other-than-temporary Impairment Losses	(4.7)	(5.0)	(1.3)	(0.4)	(3.8)	(3.6)	(4.1)	(6.2)	(11.4)	(17.7)	(50.6)
Portion of Losses Recognized in Other Comprehensive Income	0.1	0	0	0	0	(1.0)	(0.8)	3.0	0.1	1.2	0.2
Net Impairment Losses Recognized in Earnings	(4.6)	(5.0)	(1.3)	(0.4)	(3.8)	(4.6)	(4.9)	(3.2)	(11.3)	(16.5)	(50.4)
Total Revenues	613.3	592.8	647.7	641.2	670.8	650.6	657.7	663.4	2,495.0	2,642.5	2,752.1
Expenses:
Policyholders' Benefits and Incurred Losses and Loss Adjustment Expenses	376.7	399.6	477.1	392.3	407.1	403.9	419.1	417.1	1,645.7	1,647.2	1,739.5
Insurance Expenses	168.5	172.6	166.3	161.9	168.7	168.9	169.4	168.5	669.3	675.5	721.2
Write-off of Goodwill and Other Intangibles Acquired	13.5	0	0	0	0	14.8	0	0	13.5	14.8	1.5
Interest and Other Expenses	21.9	21.4	20.9	19.7	18.4	16.1	17.4	16.4	83.9	68.3	61.9
Total Expenses	580.6	593.6	664.3	573.9	594.2	603.7	605.9	602.0	2,412.4	2,405.8	2,524.1
Income from Continuing Operations before Income Taxes and Equity in Net Loss of Investee					76.6	46.9	51.8	61.4	82.6	236.7	228.0
Income Tax Expense	(6.6)	4.6	10.0	(19.7)	(20.9)	(14.3)	(14.9)	(17.4)	(11.7)	(67.5)	(59.5)
Income from Continuing Operations before Equity in Net Income (Loss) of Investee					55.7	32.6	36.9	44.0	70.9	169.2	168.5
Equity in Net Loss of Investee					0	(0.3)	(0.5)	0.7	0	(0.1)	(1.0)
Income from Continuing Operations	26.1	3.8	(6.6)	47.6	55.7	32.3	36.4	44.7	70.9	169.1	167.5
Discontinued Operations:
Income from Discontinued Operations before Income Taxes	0.2	0.6	9.3	9.4	12.1	5.6	2.5	5.6	19.5	25.8	5.6
Income Tax Expense	(0.9)	0.3	(3.2)	(2.9)	(4.9)	(2.2)	(1.1)	(2.1)	(6.7)	(10.3)	(8.4)
Income (Loss) from Discontinued Operations	(0.7)	0.9	6.1	6.5	7.2	3.4	1.4	3.5	12.8	15.5	(2.8)
Net Income (loss)	$ 25.4	$ 4.7	$ (0.5)	$ 54.1	$ 62.9	$ 35.7	$ 37.8	$ 48.2	$ 83.7	$ 184.6	$ 164.7
Income from Continuing Operations Per Unrestricted Share:
Basic	$ 0.43	$ 0.06	$ (0.11)	$ 0.78	$ 0.91	$ 0.52	$ 0.59	$ 0.72	$ 1.17	$ 2.73	$ 2.69
Diluted	$ 0.43	$ 0.06	$ (0.11)	$ 0.78	$ 0.91	$ 0.52	$ 0.59	$ 0.72	$ 1.17	$ 2.73	$ 2.69
Net Income Per Unrestricted Share:
Basic	$ 0.42	$ 0.08	$ (0.01)	$ 0.89	$ 1.03	$ 0.58	$ 0.61	$ 0.77	$ 1.38	$ 2.98	$ 2.64
Diluted	$ 0.42	$ 0.08	$ (0.01)	$ 0.89	$ 1.03	$ 0.58	$ 0.61	$ 0.77	$ 1.38	$ 2.98	$ 2.64
Dividends Paid to Shareholders Per Share	$ 0.24	$ 0.24	$ 0.24	$ 0.24	$ 0.22	$ 0.22	$ 0.22	$ 0.22	$ 0.96	$ 0.88	$ 1.07