Schedule 2 - Parent Company Financial Statements - Statements of Income (Details) (USD $) In Millions, 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
Condensed Financial Statements, Captions [Line Items]
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
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
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
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
Loss before Income Taxes and Equity in Net Income of Subsidiaries	(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)
Net Income	1.9	55.6	2.3	43.6	24.3	2.0	(3.3)	51.5	103.4	74.5	177.9
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net Investment Income									0.2	0.4	1.7
Net Realized Gains (Losses) on Sales of Investments									0.3	(0.2)	0.5
Total Revenues									0.5	0.2	2.2
Interest Expense									39.5	39.4	34.1
Other Operating Expenses									13.6	10.3	4.3
Total Expenses									53.1	49.7	38.4
Loss before Income Taxes and Equity in Net Income of Subsidiaries									(52.6)	(49.5)	(36.2)
Income Tax Benefit (Expense)									18.2	18.6	13.0
Loss Before Equity in Net Income of Subsidiaries									(34.4)	(30.9)	(23.2)
Equity in Net Income of Subsidiaries									137.8	105.4	201.1
Net Income									$ 103.4	$ 74.5	$ 177.9