Schedule of Components of Unrealized Gain (Loss) on Securities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Change in Components of Net Unrealized Gain on Securities
Change in Net Unrealized Gain on Securities	$ (7,042.9)	$ (1,301.4)	$ 983.0
Fixed Maturity Securities
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	5,949.3	7,597.6	6,364.4
Change in Net Unrealized Gain on Securities	(8,933.7)	(1,648.3)	1,233.2
End of Year Balance	(2,984.4)	5,949.3	7,597.6
Deferred Acquisition Costs
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	(70.4)	(85.1)	(62.7)
Change in Net Unrealized Gain on Securities	81.7	14.7	(22.4)
End of Year Balance	11.3	(70.4)	(85.1)
Reserve for Future Policy and Contract Benefits
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	(4,659.5)	(6,225.6)	(5,803.1)
Change in Net Unrealized Gain on Securities	5,226.2	1,566.1	(422.5)
End of Year Balance	566.7	(4,659.5)	(6,225.6)
Reinsurance Recoverable
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	132.1	200.2	424.7
Change in Net Unrealized Gain on Securities	(150.2)	(68.1)	(224.5)
End of Year Balance	(18.1)	132.1	200.2
Income Tax
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	(389.3)	(419.4)	(307.4)
Change in Net Unrealized Gain on Securities	790.0	30.1	(112.0)
End of Year Balance	400.7	(389.3)	(419.4)
Net Unrealized Gain (Loss) on Securities
Change in Components of Net Unrealized Gain on Securities
Beginning of Year Balance	962.2	1,067.7	615.9
Change in Net Unrealized Gain on Securities	(2,986.0)	(105.5)	451.8
End of Year Balance	$ (2,023.8)	$ 962.2	$ 1,067.7