CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Statement of Comprehensive Income [Abstract]
Net Income	$ 389.5	$ 392.9	$ 784.7	$ 751.2
Other Comprehensive Income (Loss)
Change in Net Unrealized Loss on Securities (net of tax expense (benefit) of $(98.0); $(155.0); $(217.2); $64.6)	(363.0)	(557.4)	(804.7)	265.8
Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy Benefits, Net of Reinsurance (net of tax expense (benefit) of $130.8; $76.1; $364.9; $(76.8))	487.0	260.1	1,360.7	(313.8)
Change in Net Gain (Loss) on Derivatives (net of tax benefit of $9.0; $10.5; $23.1; $5.8)	(37.6)	(41.1)	(90.9)	(23.7)
Change in Foreign Currency Translation Adjustment (net of tax expense of $1.2; $1.2; $1.5; $1.0)	4.2	38.3	(7.3)	63.0
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense (benefit) of $0.7; $1.5; $10.1; $(0.1))	(3.2)	(4.8)	(4.0)	0.6
Net Other Comprehensive Income (Loss)	93.8	(295.3)	461.8	(9.3)
Comprehensive Income (Loss)	$ 483.3	$ 97.6	$ 1,246.5	$ 741.9