Business Segments - Segment Net Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net Operating Income	$ 92.5	$ 12.4	$ 69.9
Income (Loss) from Continuing Operations	119.9	12.7	80.2
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Operating Income	98.6	27.4	98.4
Operating Segments [Member] | Property and Casualty Insurance [Member]
Segment Reporting Information [Line Items]
Net Operating Income	7.8	(2.9)	26.7
Operating Segments [Member] | Life and Health Insurance [Member]
Segment Reporting Information [Line Items]
Net Operating Income	90.8	30.3	71.7
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Net Operating Income	(6.1)	(15.0)	(28.5)
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit)	7.4	0.0	0.0
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Net Realized Gains on Sales of Investments	36.7	21.5	33.9
Net Impairment Losses Recognized in Earnings	(9.3)	(21.2)	(17.7)
Loss from Early Extinguishment of Debt	0.0	0.0	(5.9)
Excluding amounts attributable to Tax Law Changes [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Net Operating Income	$ (13.5)	$ (15.0)	$ (28.5)