Income From Investments - Net Realized Gains on Sales of Investments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net Investment Income [Line Items]
Realized Investment Gains									$ 99.5	$ 65.4	$ 48.3
Realized Investment Losses									(1.0)	(0.3)	(13.7)
Trading Securities Net Gains (Losses)									0.6	0.3	(0.9)
Net Realized Gains (Losses) on Sales of Investments	20.8	49.1	2.3	26.9	5.5	50.9	4.1	4.9	99.1	65.4	33.7
Fixed Maturities [Member]
Net Investment Income [Line Items]
Gains on Sales									30.9	56.9	14.2
Losses on Sales									(0.4)	(0.1)	(0.1)
Equity Securities [Member]
Net Investment Income [Line Items]
Gains on Sales									21.8	8.3	34.0
Losses on Sales									(0.5)	(0.2)	(13.5)
Investee [Member]
Net Investment Income [Line Items]
Equity Method Limited Liability Investment, Gains on Sales									2.5	0	0
Real Estate Investment [Member]
Net Investment Income [Line Items]
Real Estate, Gain on Sales									44.2	0.2	0.1
Other Investment [Member]
Net Investment Income [Line Items]
Realized Investment Gains									0.1	0	0
Realized Investment Losses									$ (0.1)	$ 0	$ (0.1)