Schedule 2 - Parent Company Financial Statements - Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Net Investment Income	$ 79.4	$ 75.9	$ 76.7	$ 70.6	$ 93.1	$ 72.3	$ 72.6	$ 71.1	$ 302.6	$ 309.1	$ 314.7
Net Realized Gains (Losses) on Sales of Investments	9.4	5.3	34.0	3.4	21.0	8.0	3.5	6.6	52.1	39.1	99.1
Net Impairment Losses Recognized in Earnings	(14.7)	(3.3)	(2.2)	(7.0)	(6.5)	(3.8)	(4.1)	(0.8)	(27.2)	(15.2)	(13.9)
Total Revenues	617.0	615.4	609.2	499.2	559.7	539.8	542.5	554.6	2,340.8	2,196.6	2,426.5
Loss from Early Extinguishment of Debt	0.0	0.0	0.0	9.1					9.1	0.0	0.0
Total Expenses	618.6	565.6	574.9	481.4	466.6	535.8	531.3	502.7	2,240.5	2,036.4	2,112.1
Income Tax Benefit	2.9	(11.8)	(6.9)	(4.3)	(29.8)	0.8	(1.9)	(16.7)	(20.1)	(47.6)	(99.9)
Net Income	$ 4.6	$ 37.9	$ 29.7	$ 13.5	$ 65.4	$ 4.7	$ 9.3	$ 35.1	85.7	114.5	217.7
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net Investment Income									1.7	0.9	0.2
Net Realized Gains (Losses) on Sales of Investments									(0.1)	(0.2)	0.6
Net Impairment Losses Recognized in Earnings									(1.6)	(1.7)	0.0
Total Revenues									0.0	(1.0)	0.8
Interest Expense									47.3	47.9	39.0
Loss from Early Extinguishment of Debt									9.1	0.0	0.0
Other Operating Expenses									17.6	2.7	21.6
Total Expenses									74.0	50.6	60.6
Loss before Income Taxes and Equity in Net Income of Subsidiaries									(74.0)	(51.6)	(59.8)
Income Tax Benefit									26.5	18.9	20.8
Loss before Equity in Net Income of Subsidiaries									(47.5)	(32.7)	(39.0)
Equity in Net Income of Subsidiaries									133.2	147.2	256.7
Net Income									$ 85.7	$ 114.5	$ 217.7