STATEMENT OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Statement of Comprehensive Income [Abstract]
Change in Net Unrealized Loss on Securities, Tax Expense (Benefit)	$ 38.6	$ 22.0	$ (77.5)	$ 132.2
OCI, Liability for Future Policy Benefit, Gain (Loss), after REclassification Adjustment, Tax	(59.9)	10.9	66.0	(31.7)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax	0.8	(15.9)	(0.2)	(4.2)
Change in Foreign Currency Translation Adjustment, Tax Expense (Benefit)	(0.3)	(0.4)	(0.4)	(0.2)
Change in Unrecognized Pension and Postretirement Benefit costs, Tax Expense	$ (0.5)	$ 0.5	$ (1.5)	$ 0.7