Investments (Schedule of Realized Gain (Loss)) (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]
Gain (Loss) on Investments [Line Items]
Proceeds from Sales	$ 94.2	$ 145.2	$ 402.1	$ 969.9
Gross Gains	3.6	0.7	9.5	13.6
Gross Losses	0.3	0.6	4.5	5.3
Equity Securities [Member]
Gain (Loss) on Investments [Line Items]
Proceeds from Sales	20.7	17.4	194.1	185.2
Gross Gains		4.1	26.4	24.2
Gross Losses	$ 1.2	$ 0.1	$ 2.9	$ 0.1