STATEMENT OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Change in Net Unrealized Gain on Securities Before Adjustment, Tax Expense (Benefit)	$ 300.6	$ (1,890.8)	$ (346.9)
OCI, Liability for Future Policy Benefit, Gain (Loss), after Reclassification Adjustment, Tax	(256.5)	2,385.1	622.8
Change in Net Gain (Loss) on Hedges, Tax Benefit	(17.0)	(19.2)	(9.8)
Other Comprehensive Income (Loss), Foreign Currency Translation, Tax Expense (Benefit)	0.9	(0.1)	4.2
Change in Unrecognized Pension and Postretirement Benefit Costs, Tax Expense (Benefit)	$ (2.7)	$ 18.9	$ 42.1