CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net Income	$ 395.2	$ 358.3
Other Comprehensive Income (Loss)
Change in Net Unrealized Loss on Securities (net of tax expense (benefit) of $(119.2); $219.6)	(441.7)	823.2
Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy Benefits, Net of Reinsurance (net of tax expense (benefit) of $234.1; $(152.9))	873.7	(573.9)
Change in Net Gain (Loss) on Derivatives (net of tax expense (benefit) of $(14.1); $4.7)	(53.3)	17.4
Change in Foreign Currency Translation Adjustment (net of tax expense (benefit) of $0.3; $(0.2))	(11.5)	24.7
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense (benefit) of $9.4; $(1.6))	(0.8)	5.4
Total Other Comprehensive Income	368.0	286.0
Comprehensive Income	$ 763.2	$ 644.3