Basis of Presentation (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended			0 Months Ended	3 Months Ended			3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Jan. 02, 2012 Accounting Standards Update 2010-26 [Member]	Mar. 31, 2012 Accounting Standards Update 2010-26 [Member] As Computed without Change in Accounting [Member]	Mar. 31, 2011 Accounting Standards Update 2010-26 [Member] As Originally Reported [Member]	Dec. 31, 2011 Accounting Standards Update 2010-26 [Member] As Originally Reported [Member]	Mar. 31, 2012 Accounting Standards Update 2010-26 [Member] Effect of Change [Member]	Mar. 31, 2011 Accounting Standards Update 2010-26 [Member] Effect of Change [Member]	Dec. 31, 2011 Accounting Standards Update 2010-26 [Member] Effect of Change [Member]
Accounting Policy Disclosures [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets				$ (99.5)
Impact on Assets:
Deferred Policy Acquisition Costs	297.9		294.0		455.8		448.5	(157.9)		(154.5)
Current and Deferred Income Tax Assets	0		6.4				3.1			3.3
Total Assets	7,970.4		7,934.7		8,128.3		8,085.9	(157.9)		(151.2)
Impact on Liabilities and Shareholders' Equity:
Liabilities for Income Taxes	18.2		6.2		74.4		57.9	(56.2)		(51.7)
Total Liabilities	5,838.6		5,818.1		5,894.8		5,869.8	(56.2)		(51.7)
Retained Earnings	1,126.2		1,108.7		1,227.9		1,208.2	(101.7)		(99.5)
Total Shareholders' Equity	2,131.8		2,116.6		2,233.5		2,216.1	(101.7)		(99.5)
Total Liabilities and Shareholders' Equity	7,970.4		7,934.7		8,128.3		8,085.9	(157.9)		(151.2)
Income Statement [Abstract]
Total Revenues	611.2	641.2			611.2	641.2		0	0
Expenses:
Policyholders' Benefits and Incurred Losses and Loss Adjustment Expenses	376.6	392.3			376.6	392.3		0	0
Insurance Expenses	162.4	166.1			159.0	161.9		3.4	4.2
Interest and Other Expenses	21.8	19.7			21.8	19.7		0	0
Total Expenses	560.8	578.1			557.4	573.9		3.4	4.2
Income from Continuing Operations before Income Taxes	50.4	63.1			53.8	67.3		(3.4)	(4.2)
Income Tax Expense	(14.1)	(18.1)			(15.3)	(19.7)		1.2	1.6
Income from Continuing Operations	36.3	45.0			38.5	47.6		(2.2)	(2.6)
Income from Discontinued Operations	7.3	6.5			7.3	6.5		0	0
Net Income	43.6	51.5			45.8	54.1		(2.2)	(2.6)
Total Comprehensive Income	47.7	35.7			49.9	38.3		(2.2)	(2.6)
Net Income Per Unrestricted Share:
Basic (in dollars per share)	$ 0.61	$ 0.74			$ 0.64	$ 0.78		$ (0.03)	$ (0.04)
Diluted (in dollars per share)	$ 0.60	$ 0.73			$ 0.64	$ 0.78		$ (0.04)	$ (0.05)
Income from Continuing Operations per Unrestricted Share:
Basic (in dollars per share)	$ 0.73	$ 0.85			$ 0.76	$ 0.89		$ (0.03)	$ (0.04)
Diluted (in dollars per share)	$ 0.72	$ 0.84			$ 0.76	$ 0.89		$ (0.04)	$ (0.05)
Impact on Operating Activities:
Net Income	43.6	51.5			45.8	54.1		(2.2)	(2.6)
Increase in Deferred Policy Acquisition Costs	(3.9)	(3.5)			(7.3)	(7.7)		3.4	4.2
Change in Income Taxes	16.2	37.9			17.4	39.5		(1.2)	(1.6)
Net Cash Provided by Operating Activities	$ 55.6	$ 73.2