CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Statement of Comprehensive Income [Abstract]
Net Income	$ 232.0	$ 189.1
Other Comprehensive Income (Loss)
Change in Net Unrealized Loss on Securities (net of tax expense (benefit) of $(116.1); $110.2)	(429.2)	422.0
Change in the Effect of Discount Rate Assumptions on the Liability for Future Policy Benefits, Net of Reinsurance (net of tax expense (benefit) of $125.9; $(42.6))	465.2	(166.3)
Change in Net Loss on Derivatives (net of tax expense (benefit) of $(1.0); $11.7)	(3.3)	45.5
Change in Foreign Currency Translation Adjustment (net of tax expense (benefit) of $0.1; $(0.2))	(23.0)	42.3
Change in Unrecognized Pension and Postretirement Benefit Costs (net of tax expense (benefit) of $1.0; $(0.2))	(3.3)	(1.4)
Total Other Comprehensive Income	13.0	344.9
Comprehensive Income	$ 245.0	$ 534.0