CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Statement of Financial Position [Abstract]
Fixed maturities, available for sale, amortized cost	$ 6,147.4	$ 6,026.7
Equity securities at cost	$ 56.2	$ 56.2
Preferred stock, par value (in usd per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in usd per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	75,000,000	75,000,000
Common stock, shares issued (in shares)	67,467,590	67,323,929
Treasury stock (in shares)	27,086,418	26,664,472