CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Statement of Comprehensive Income [Abstract]
Net Income	$ 335.6	$ 389.5	$ 524.7	$ 784.7
Other Comprehensive Income (Loss)
Change in Net Unrealized Loss on Securities (net of tax expense (benefit) of $22.0; $(98.0); $132.2; $(217.2))	79.5	(363.0)	501.5	(804.7)
Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy Benefits, Net of Reinsurance (net of tax expense (benefit) of $10.9; $130.8; $(31.7); $364.9)	39.8	487.0	(126.5)	1,360.7
Change in Net Loss on Derivatives (net of tax benefit of $15.9; $9.0; $4.2; $23.1)	(59.8)	(37.6)	(14.3)	(90.9)
Change in Foreign Currency Translation Adjustment (net of tax expense of $0.4; $1.2; $0.2; $1.5)	80.0	4.2	122.3	(7.3)
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense (benefit) of $(0.5); $0.7; $(0.7); $10.1)	1.4	(3.2)	0.0	(4.0)
Net Other Comprehensive Income	138.1	93.8	483.0	461.8
Comprehensive Income	$ 473.7	$ 483.3	$ 1,007.7	$ 1,246.5