Investments - Schedule of Other Than Temporary Impairment (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Reductions due to Intent to Sell Investments	$ 0	$ (2.5)	$ 0	$ (2.5)
Fixed Maturities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance at Beginning of Period	2.3	5.6	2.4	3.7
Additions for Previously Unrecognized OTTI Credit Losses	0	0	0	3.1
Increases to Previously Recognized OTTI Credit Losses	0	2.5	0	2.6
Reductions to Previously Recognized OTTI Credit Losses	(0.2)	(0.2)	(0.3)	(1.5)
Balance at End of Period	$ 2.1	$ 5.4	$ 2.1	$ 5.4