Investments (Proceeds and Realized Gains Losses From Investments) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Investments [Abstract]
Proceeds	$ 2,038.2	$ 5,442.0	$ 6,999.6	$ 10,874.6
Gross realized gains	32.4	176.0	221.5	354.9
Gross realized losses	$ (6.7)	$ (80.6)	$ (88.3)	$ (188.5)