Income From Investments - Net Impairment Losses Recognized in Earnings (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
Net Investment Income [Line Items]
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)
Fixed Maturities [Member]
Net Investment Income [Line Items]
Net Impairment Losses Recognized in Earnings									(5.7)	(10.3)	(1.9)
Equity Securities [Member]
Net Investment Income [Line Items]
Net Impairment Losses Recognized in Earnings									(7.1)	(3.6)	(1.9)
Real Estate [Member]
Net Investment Income [Line Items]
Net Impairment Losses Recognized in Earnings									$ (2.4)	$ 0	$ (3.1)