Investments - Schedule of Other Than Temporary Impairment (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
From Status of Credit Loss to Status of Intent-to-sell or Required-to-sell	$ 2.1	$ 0
Fixed Maturities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance at Beginning of Period	4.4	3.6	4.6	3.9
Additions for Previously Unrecognized OTTI Credit Losses	0.8	0	1.8	0
Increases to Previously Recognized OTTI Credit Losses	1.3	0	1.3	0
Reductions to Previously Recognized OTTI Credit Losses	0	0	0	(0.1)
From Status of Credit Loss to Status of Intent-to-sell or Required-to-sell			3.2	0
Reductions for Investments Sold During Period	0	0	(0.1)	(0.2)
Balance at End of Period	$ 4.4	$ 3.6	$ 4.4	$ 3.6