CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Statement of Comprehensive Income [Abstract]
Net Income	$ 1,779.1	$ 1,283.8	$ 1,407.2
Other Comprehensive Income (Loss)
Change in Net Unrealized Gain (Loss) on Securities (net of tax expense (benefit) of $(226.6); $300.6; $(1,890.8))	(836.1)	1,109.3	(7,042.8)
Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy Benefits, Net of Reinsurance (net of tax expense (benefit) of $488.9; $(256.5); $2,385.1)	1,833.8	(962.3)	8,884.6
Change in Net Gain (Loss) on Derivatives (net of tax benefit of $51.5; $17.0; $19.2)	(197.0)	(64.1)	(71.4)
Change in Foreign Currency Translation Adjustment (net of tax expense (benefit) of $1.1; $0.9; $(0.1))	(21.9)	69.0	(116.0)
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense (benefit) of $12.0; $(2.7); $18.9)	(5.5)	11.6	(61.9)
Total Other Comprehensive Income	784.3	140.3	1,716.3
Comprehensive Income	$ 2,563.4	$ 1,424.1	$ 3,123.5