Investments (Details 5) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Other-Than-Temporary Impairment Credit Losses Recognized in Net Income - Rollforward
Beginning balance	$ (235.4)	$ (335.2)
Credit losses for which an other-than-temporary impairment was not previously recognized	(0.3)	(4.3)
Credit losses for which an other-than-temporary impairment was previously recognized	(24.1)	(18.3)
Reduction for credit losses previously recognized on fixed maturities now sold, paid down or intended to be sold	33.6	35.8
Net reduction (increase) for positive changes in cash flows expected to be collected and amortization	2.0	3.4
Ending balance	$ (224.2)	$ (318.6)