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, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Trading Securities Net Gains (Losses)									$ 0.3	$ (0.9)	$ 0.5
Net Realized Gains (Losses) on Sales of Investments	5.5	50.9	4.1	4.9	5.9	(4.2)	17.8	14.2	65.4	33.7	42.6
Fixed Maturities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gains on Sales									56.9	14.2	21.5
Losses on Sales									(0.1)	(0.1)	(0.1)
Equity Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gains on Sales									8.3	34.0	11.7
Losses on Sales									(0.2)	(13.5)	0
Investee [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gain on Sales - Intermec									0	0	0.8
Real Estate Investment [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gains on Sales - Real Estate									0.2	0.1	8.2
Other Investment [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gains on Sales - Other Investments									0	0	0.1
Losses on Sales - Other Investments									$ 0	$ (0.1)	$ (0.1)