Investments - Net Realized Gains on Sales of Investments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Fixed Maturities [Member]
Net Investment Income [Line Items]
Realized Gains	$ 2.7	$ 3.6	$ 14.1	$ 9.5
Realized Losses	(0.8)	(0.1)	(1.1)	(0.7)
Equity Securities [Member]
Net Investment Income [Line Items]
Realized Gains	9.3	2.8	9.8	35.7
Realized Losses	$ 0.0	$ (0.7)	$ (0.1)	$ (1.4)