CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net Income	$ 645.7	$ 202.0	$ 1,430.4	$ 953.2
Other Comprehensive Income (Loss)
Change in Net Unrealized Loss on Securities (net of tax expense (benefit) of $327.6; $(313.8); $110.4; $(249.2))	1,232.6	(1,185.8)	427.9	(920.0)
Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy Benefits, Net of Reinsurance (net of tax expense (benefit) of $(329.3); $445.0; $35.6; $368.2)	(1,239.3)	1,688.4	121.4	1,374.6
Change in Net Loss on Derivatives (net of tax expense (benefit) of $14.1; $(38.9); $(9.0); $(44.7))	55.7	(144.4)	(35.2)	(168.1)
Change in Foreign Currency Translation Adjustment (net of tax expense (benefit) of $—; $(0.7); $1.5; $0.3)	68.5	(55.1)	61.2	7.9
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense (benefit) of $(0.3); $1.2; $9.8; $1.1)	1.0	(3.9)	(3.0)	(3.3)
Net Other Comprehensive Income	116.5	307.0	578.3	297.7
Comprehensive Income	$ 762.2	$ 509.0	$ 2,008.7	$ 1,250.9