CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Investments
Amortized Cost of Fixed Maturity Securities	$ 35,530.8	$ 34,747.2
Debt Securities, Available-for-sale, Allowance for credit losses for Fixed Maturity Securities	0.0	5.9
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	15.3	15.9
Other Assets
Premium Receivable, Allowance for Credit Loss	26.9	26.1
Reinsurance Recoverable, Allowance for Credit Loss	$ 0.4	$ 1.4
Stockholders' Equity, Number of Shares, Par Value and Other Disclosure [Abstract]
Common Stock, Par Value (in dollars per share)	$ 0.10	$ 0.10
Common Stock, Shares Authorized	725,000,000	725,000,000
Common Stock, Shares Issued	196,635,349	196,194,941
Treasury Stock, Shares at Cost	35,885,782	30,500,524