Schedule of Components of Unrealized Gain (Loss) on Securities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Change in Components of Net Unrealized Gain on Securities
Change in Net Unrealized Gain (Loss) on Securities	$ 1,439.3	$ (2,101.2)	$ 918.8
Fixed Maturity Securities
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	4,054.8	7,221.5
Change in Net Unrealized Gain (Loss) on Securities	2,206.7	(3,166.7)
End of Period Balance	6,261.5	4,054.8
Other Investments
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	55.5	92.8
Change in Net Unrealized Gain (Loss) on Securities	(41.6)	(37.3)
End of Period Balance	13.9	55.5
Deferred Acquisition Costs
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	(41.6)	(67.0)
Change in Net Unrealized Gain (Loss) on Securities	(9.2)	25.4
End of Period Balance	(50.8)	(41.6)
Reserve for Future Policy and Contract Benefits
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	(4,108.5)	(6,277.5)
Change in Net Unrealized Gain (Loss) on Securities	(2,041.8)	2,169.0
End of Period Balance	(6,150.3)	(4,108.5)
Reinsurance Recoverable
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	263.8	351.5
Change in Net Unrealized Gain (Loss) on Securities	101.2	(87.7)
End of Period Balance	365.0	263.8
Deferred Income Tax Charges
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	(88.3)	(447.8)
Change in Net Unrealized Gain (Loss) on Securities	(60.7)	359.5
End of Period Balance	(149.0)	(88.3)
Net Unrealized Gain on Securities
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	135.7	873.5
Change in Net Unrealized Gain (Loss) on Securities	154.6	(737.8)
End of Period Balance	$ 290.3	$ 135.7