CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Statement of Comprehensive Income [Abstract]
Net Income	$ 738.5	$ 1,779.1	$ 1,283.8
Other Comprehensive Income (Loss)
Change in Net Unrealized Loss on Securities (net of tax expense (benefit) of $200.4; $(226.6); $300.6)	752.1	(836.1)	1,109.3
Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy Benefits, Net of Reinsurance (net of tax expense (benefit) of $(66.2); $488.9; $(256.5))	(255.5)	1,833.8	(962.3)
Change in Net Loss on Derivatives (net of tax benefit of $3.1; $51.5; $17.0)	(8.1)	(197.0)	(64.1)
Change in Foreign Currency Translation Adjustment (net of tax expense of $0.1; $1.1; $0.9)	97.4	(21.9)	69.0
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense (benefit) of $35.6; $12.0; $(2.7))	(129.3)	(5.5)	11.6
Total Other Comprehensive Income	715.2	784.3	140.3
Comprehensive Income	$ 1,453.7	$ 2,563.4	$ 1,424.1