Schedule 2 - Parent Company Financial Statements - Statements of Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net Investment Income	$ 93.1	$ 72.3	$ 72.6	$ 71.1	$ 76.9	$ 82.4	$ 74.6	$ 80.8	$ 309.1	$ 314.7	$ 295.9
Net Realized Gains (Losses) on Sales of Investments	21.0	8.0	3.5	6.6	20.8	49.1	2.3	26.9	39.1	99.1	65.4
Net Impairment Losses Recognized in Earnings	(6.5)	(3.8)	(4.1)	(0.8)	(7.6)	(3.4)	(1.0)	(1.9)	(15.2)	(13.9)	(6.9)
Total Revenues	559.7	539.8	542.5	554.6	586.0	635.7	588.9	615.9	2,196.6	2,426.5	2,462.3
Total Expenses	466.6	535.8	531.3	502.7	504.6	533.7	542.5	531.3	2,036.4	2,112.1	2,339.9
Income Tax Benefit	(29.8)	0.8	(1.9)	(16.7)	(26.6)	(33.4)	(13.9)	(26.0)	(47.6)	(99.9)	(30.6)
Net Income	65.4	4.7	9.3	35.1	55.2	70.1	34.0	58.4	114.5	217.7	103.4
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net Investment Income									0.9	0.2	0.2
Net Realized Gains (Losses) on Sales of Investments									(0.2)	0.6	0.3
Net Impairment Losses Recognized in Earnings									(1.7)	0	0
Total Revenues									(1.0)	0.8	0.5
Interest Expense									47.9	39.0	39.5
Other Operating Expenses									2.7	21.6	13.6
Total Expenses									50.6	60.6	53.1
Loss before Income Taxes and Equity in Net Income of Subsidiaries									(51.6)	(59.8)	(52.6)
Income Tax Benefit									18.9	20.8	18.2
Loss before Equity in Net Income of Subsidiaries									(32.7)	(39.0)	(34.4)
Equity in Net Income of Subsidiaries									147.2	256.7	137.8
Net Income									$ 114.5	$ 217.7	$ 103.4