Schedule of Components of Unrealized Gain (Loss) on Securities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Change in Components of Net Unrealized Gain on Securities
Change in Net Unrealized Gain on Securities	$ (260.8)	$ 481.4	$ (1,048.0)	$ 1,322.4
Fixed Maturity Securities
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	6,603.1	7,422.8	7,597.6	6,364.4
Change in Net Unrealized Gain on Securities	(329.8)	608.0	(1,324.3)	1,666.4
End of Period Balance	6,273.3	8,030.8	6,273.3	8,030.8
Deferred Acquisition Costs
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	(79.8)	(69.4)	(85.1)	(62.7)
Change in Net Unrealized Gain on Securities	6.8	(5.8)	12.1	(12.5)
End of Period Balance	(73.0)	(75.2)	(73.0)	(75.2)
Reserve for Future Policy and Contract Benefits
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	(5,386.6)	(6,459.8)	(6,225.6)	(5,803.1)
Change in Net Unrealized Gain on Securities	242.7	(511.5)	1,081.7	(1,168.2)
End of Period Balance	(5,143.9)	(6,971.3)	(5,143.9)	(6,971.3)
Reinsurance Recoverable
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	152.8	464.5	200.2	424.7
Change in Net Unrealized Gain on Securities	(14.6)	87.4	(62.0)	127.2
End of Period Balance	138.2	551.9	138.2	551.9
Income Tax
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	(378.1)	(395.0)	(419.4)	(307.4)
Change in Net Unrealized Gain on Securities	19.5	(36.7)	60.8	(124.3)
End of Period Balance	(358.6)	(431.7)	(358.6)	(431.7)
Net Unrealized Gain on Securities
Change in Components of Net Unrealized Gain on Securities
Beginning of Period Balance	911.4	963.1	1,067.7	615.9
Change in Net Unrealized Gain on Securities	(75.4)	141.4	(231.7)	488.6
End of Period Balance	$ 836.0	$ 1,104.5	$ 836.0	$ 1,104.5