Schedule of Components of Unrealized Gain (Loss) on Securities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Change in Components of Net Unrealized Gain on Securities
Change in Net Unrealized Gain on Securities	$ 277.2	$ (168.5)	$ 1,999.2	$ (1,085.4)
Fixed Maturity Securities
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	6,299.5	4,901.2	3,695.7	6,261.5
Change in Net Unrealized Gain on Securities	390.9	(237.8)	2,994.7	(1,598.1)
End of Period Balance	6,690.4	4,663.4	6,690.4	4,663.4
Other Investments
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	(21.3)	(14.8)	(33.7)	13.9
Change in Net Unrealized Gain on Securities	0.2	(20.3)	12.6	(49.0)
End of Period Balance	(21.1)	(35.1)	(21.1)	(35.1)
Deferred Acquisition Costs
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	(52.5)	(41.8)	(29.4)	(50.8)
Change in Net Unrealized Gain on Securities	(3.6)	1.8	(26.7)	10.8
End of Period Balance	(56.1)	(40.0)	(56.1)	(40.0)
Reserve for Future Policy and Contract Benefits
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	(5,578.6)	(4,981.6)	(3,578.4)	(6,150.3)
Change in Net Unrealized Gain on Securities	(196.9)	331.9	(2,197.1)	1,500.6
End of Period Balance	(5,775.5)	(4,649.7)	(5,775.5)	(4,649.7)
Reinsurance Recoverable
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	366.0	312.9	263.2	365.0
Change in Net Unrealized Gain on Securities	13.7	(4.8)	116.5	(56.9)
End of Period Balance	379.7	308.1	379.7	308.1
Income Tax
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	(352.0)	(63.8)	(113.1)	(149.0)
Change in Net Unrealized Gain on Securities	(62.2)	(24.3)	(301.1)	60.9
End of Period Balance	(414.2)	(88.1)	(414.2)	(88.1)
Net Unrealized Gain on Securities
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	661.1	112.1	204.3	290.3
Change in Net Unrealized Gain on Securities	142.1	46.5	598.9	(131.7)
End of Period Balance	$ 803.2	$ 158.6	$ 803.2	$ 158.6